{"id":98,"date":"2018-11-16T05:58:34","date_gmt":"2018-11-16T05:58:34","guid":{"rendered":"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/?post_type=chapter&#038;p=98"},"modified":"2018-11-16T09:38:32","modified_gmt":"2018-11-16T09:38:32","slug":"calculation-of-density-of-states-dos","status":"publish","type":"chapter","link":"https:\/\/ebooks.inflibnet.ac.in\/phy12\/chapter\/calculation-of-density-of-states-dos\/","title":{"rendered":"Calculation of Density of States (DOS)"},"content":{"raw":"<div>\r\n\r\n&nbsp;\r\n\r\n3.3.1\u00a0\u00a0\u00a0\u00a0 DOS in 3D\r\n\r\n3.3.2\u00a0\u00a0\u00a0\u00a0 DOS in 2D\r\n\r\n3.3.3\u00a0\u00a0\u00a0\u00a0 DOS in 1D\r\n\r\n3.3.4\u00a0\u00a0\u00a0 DOS in 0D\r\n\r\n<\/div>\r\n<div>\r\n\r\n&nbsp;\r\n\r\n<strong>CALCULATION OF DENSITY OF STATES (DOS): Quantum Wells, Wires and Dots<\/strong>\r\n\r\n&nbsp;\r\n\r\n<strong style=\"font-size: 1em\">3.3.1 DOS for 3 dimensions (Bulk)<\/strong>\r\n\r\n&nbsp;\r\n\r\n<span style=\"text-align: initial;font-size: 1em\">Consider the volume in \"k\" space<\/span>\r\n\r\n<img class=\"size-full wp-image-107 aligncenter\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-42.png\" alt=\"\" width=\"76\" height=\"33\" \/>\r\n\r\nwhere for a particle in this space\r\n\r\n<\/div>\r\n<div><img class=\"aligncenter size-full wp-image-108\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-43.png\" alt=\"\" width=\"235\" height=\"46\" \/><\/div>\r\n<div>\r\n\r\n<img class=\"aligncenter size-full wp-image-101\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-37.png\" alt=\"\" width=\"578\" height=\"374\" \/>\r\n<p style=\"text-align: center\">Figure . Electron state is defined by a point in k-space.<\/p>\r\n&nbsp;\r\n\r\n&nbsp;\r\n<p style=\"text-align: justify\">Note that the 2 \u00a0arises from the constraints of periodic boundary conditions as proposed to the more general where <em>n<\/em>=0, 1, 2, 3... The volume of a given mode is then= . The number of modes (<em>N<\/em>) in the sphere is,<\/p>\r\n<img class=\"aligncenter size-full wp-image-109\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-44.png\" alt=\"\" width=\"195\" height=\"46\" \/>\r\n\r\nSay the particle in an electron and we consider spin (up and down), then we multiply <em>N<\/em> by 2.\r\n\r\n<img class=\"aligncenter size-full wp-image-110\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-45.png\" alt=\"\" width=\"220\" height=\"96\" \/>\r\n\r\nis the total number of states in sphere. Now consider the density\r\n\r\n<img class=\"aligncenter size-full wp-image-111\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-46.png\" alt=\"\" width=\"493\" height=\"304\" \/>\r\n\r\n&nbsp;\r\n\r\n<\/div>\r\n<div>\r\n\r\n<img class=\"aligncenter size-full wp-image-104\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-40.png\" alt=\"\" width=\"396\" height=\"195\" \/>\r\n<p style=\"text-align: center\">Figure . Density of states in 3 dimension (Eq.3.48)<\/p>\r\n&nbsp;\r\n\r\n&nbsp;\r\n\r\n<strong>3.3.2 DOS in Two Dimensions (well)<\/strong>\r\n\r\n&nbsp;\r\n<p style=\"text-align: justify\">Here we have 1D that is quantized. Let's us assume it is the z-direction. The total energy of this system is a sum of the energy along the quantized direction plus the energy along the other 2 free directions. It is expressed as<\/p>\r\n<img class=\"aligncenter size-full wp-image-112\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-47.png\" alt=\"\" width=\"436\" height=\"100\" \/>\r\n\r\n&nbsp;\r\n\r\nwhere for the particle\r\n\r\n<\/div>\r\n<div>\r\n\r\n<img class=\"aligncenter size-full wp-image-113\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-48.png\" alt=\"\" width=\"74\" height=\"111\" \/>\r\n\r\nThe area of a given mode is then ???? with the total number of modes (N) in the area being\r\n\r\n<img class=\"aligncenter size-full wp-image-114\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-49.png\" alt=\"\" width=\"185\" height=\"50\" \/>\r\n\r\nAgain if the particle is an electron and we consider spin, multiply by 2 to get\r\n\r\n<img class=\"aligncenter size-full wp-image-115\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-50.png\" alt=\"\" width=\"183\" height=\"48\" \/>\r\n<p style=\"text-align: justify\"><span style=\"text-align: initial;text-indent: 1em;font-size: 1em\">This is the energy density of the sub-band for a given or (<\/span><em style=\"text-align: initial;text-indent: 1em;font-size: 1em\">E<\/em><em style=\"text-align: initial;text-indent: 1em;font-size: 1em\">n<\/em><span style=\"text-align: initial;text-indent: 1em;font-size: 1em\">). For each successive there will be an additional \u045b2 and hence another subband. Therefore the density of the states is written<\/span><\/p>\r\n<img class=\"aligncenter size-full wp-image-116\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-51.png\" alt=\"\" width=\"162\" height=\"40\" \/>\r\n\r\n<span style=\"font-size: 1em;text-align: initial;text-indent: 1em\">Where \u0472 is the heavy side function.<\/span>\r\n\r\n<\/div>\r\n<div>\r\n\r\n<img class=\"aligncenter size-full wp-image-117\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-52.png\" alt=\"\" width=\"294\" height=\"232\" \/>\r\n<p style=\"text-align: center\"><span style=\"text-align: initial;font-size: 1em\">Figure Density of states in 2 dimension. Shaded area presents occupied states.<\/span><\/p>\r\n\r\n<\/div>\r\n<div>\r\n\r\n&nbsp;\r\n\r\n<strong>3.3.3 DOS in One Dimensions (Wire)<\/strong>\r\n\r\n&nbsp;\r\n\r\nConsider now the situation where there are two dimensions confined and only 1 degree of freedom (say the x-direction). The total energy of the system can be written as\r\n\r\n<img class=\"aligncenter size-full wp-image-118\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-53.png\" alt=\"\" width=\"508\" height=\"117\" \/><img class=\"aligncenter size-full wp-image-119\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-54.png\" alt=\"\" width=\"680\" height=\"115\" \/><img class=\"aligncenter size-full wp-image-120\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-55.png\" alt=\"\" width=\"699\" height=\"377\" \/><img class=\"aligncenter size-full wp-image-121\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-56.png\" alt=\"\" width=\"295\" height=\"190\" \/>\r\n\r\n<\/div>\r\n<div>\r\n<p style=\"text-align: center\">Figure Density of states in 1 dimension. Shaded area presents occupied states.<\/p>\r\n&nbsp;\r\n\r\n&nbsp;\r\n\r\n<strong>3.3.4 Zero dimensions (Quantum Dot)<\/strong>\r\n\r\n&nbsp;\r\n<p style=\"text-align: justify\">Here since all three dimensions are confined. The density of states is basically a series of delta functions. The total energy of the system is<\/p>\r\n\r\n<\/div>\r\n<div>\r\n\r\n<img class=\"aligncenter size-full wp-image-122\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-57.png\" alt=\"\" width=\"649\" height=\"215\" \/><img class=\"aligncenter size-full wp-image-123\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-58.png\" alt=\"\" width=\"578\" height=\"247\" \/>\r\n\r\n&nbsp;\r\n\r\n<strong>3.3.5 More density of states<\/strong>\r\n\r\n&nbsp;\r\n\r\n<strong>Density of states in the conduction band<\/strong>\r\n\r\n&nbsp;\r\n<p style=\"text-align: justify\">For this we need to know the probability that an electron will occupy a given stats of energy E. The Probability, P(E), is referred as the Fermi Dirac distribution. In addition we need to know the density of states ( \u2032). The density of states has units of number of unit volume per unit energy. Therefore \u2032 is the number of states per unit volume. The number of occupied states at a given energy per unit volume is therefore<\/p>\r\n<img class=\"aligncenter size-full wp-image-124\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-59.png\" alt=\"\" width=\"186\" height=\"34\" \/>\r\n\r\nHere\u00a0 \u00a0is the Fermi energy.\r\n\r\n<img class=\"aligncenter size-full wp-image-125\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-60.png\" alt=\"\" width=\"141\" height=\"50\" \/>\r\n\r\nthe total concentration of electrons in the conduction band is therefore the integral over all available energies\r\n\r\n<img class=\"aligncenter size-full wp-image-126\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-61.png\" alt=\"\" width=\"182\" height=\"38\" \/>\r\n\r\nwhere?<sub>c<\/sub> is the energy where conduction band starts. For the case of three dimensional material\r\n\r\n<img class=\"aligncenter size-full wp-image-127\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-62.png\" alt=\"\" width=\"160\" height=\"42\" \/>\r\n\r\nTaking account into conduction band begins, the density of states can be written as\r\n\r\n&nbsp;\r\n\r\n<\/div>\r\n<div>\r\n\r\n<img class=\"aligncenter size-full wp-image-128\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-63.png\" alt=\"\" width=\"627\" height=\"116\" \/>\r\n\r\nThe integral is called the Fermi integral or Fermi Dirac integral.\r\n\r\n&nbsp;\r\n\r\nConsider the case where, E\u00a0 \u2212 E<sub>r\u00a0<\/sub>\u226b KTand the Fermi Dirac distribution function becomes\r\n\r\n<\/div>\r\n<div><img class=\"aligncenter size-full wp-image-129\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-64.png\" alt=\"\" width=\"640\" height=\"483\" \/><\/div>\r\n<div>\r\n\r\n&nbsp;\r\n\r\n<strong><em>This is the expression for the effective density of states of the conduction band.<\/em><\/strong>\r\n\r\n&nbsp;\r\n\r\n<strong>Density of states in the valance band<\/strong>\r\n\r\n&nbsp;\r\n\r\nThe number of holes at a given energy per unit volume is given as\r\n\r\n<\/div>\r\n<div><\/div>\r\n<div>\r\n\r\n<img class=\"aligncenter size-full wp-image-130\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-65.png\" alt=\"\" width=\"524\" height=\"231\" \/>\r\n<p style=\"text-align: justify\">Where Ev is the energy where valance band starts. The total concentration of holes in the valance band is the integral over all energies.<\/p>\r\n<img class=\"aligncenter size-full wp-image-131\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-66.png\" alt=\"\" width=\"657\" height=\"499\" \/>\r\n\r\n&nbsp;\r\n<p style=\"text-align: justify\"><span style=\"font-size: 1em;text-align: initial\">This is the effective density of the states in the valance band.<\/span><\/p>\r\n\r\n<\/div>\r\n<div>\r\n\r\n&nbsp;\r\n\r\n<strong>Summary<\/strong>\r\n\r\n&nbsp;\r\n<p style=\"text-align: justify\">Fermi level of an intrinsic semiconductor\u00a0 If the bulk semiconductor is intrinsic, there has been no doping of the material and hence no extra electrons or holes anywhere. in this situation<\/p>\r\n<img class=\"aligncenter size-full wp-image-132\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-67.png\" alt=\"\" width=\"464\" height=\"192\" \/>\r\n<p style=\"text-align: justify\"><strong><em>One can therefore see that at T=0 the Fermi energy of an intrinsic semiconductor is at the halfway point between the top of the valance band and the bottom of the conduction band.<\/em><\/strong><\/p>\r\n&nbsp;\r\n\r\n<strong>Density of states in the conduction band<\/strong>\r\n\r\n&nbsp;\r\n\r\nWe start with the Fermi Dirac distribution for electrons and also the density of states\r\n\r\n<img class=\"aligncenter size-full wp-image-133\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-68.png\" alt=\"\" width=\"174\" height=\"35\" \/>Consider only one of the subband. In this case the density of states simplifies to\r\n\r\n<img class=\"aligncenter size-full wp-image-134\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-69.png\" alt=\"\" width=\"98\" height=\"36\" \/>\r\n\r\n<\/div>\r\n<div>\r\n\r\n<span style=\"text-align: initial;font-size: 1em\">Now recall from the previous section that the number of states at a given energy per unit volume<\/span><img class=\"aligncenter size-full wp-image-135\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-70.png\" alt=\"\" width=\"194\" height=\"26\" \/>\r\n<p style=\"text-align: justify\">the total concentration of electrons in this first subband is the integral over all available energies. Rather than use ntot as before let's just stick to <em>n<\/em><em>c<\/em> from the start<\/p>\r\n<img class=\"aligncenter size-full wp-image-136\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-71.png\" alt=\"\" width=\"495\" height=\"91\" \/>\r\n\r\n<\/div>\r\n<div>\r\n\r\n<img class=\"aligncenter size-full wp-image-137\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-72.png\" alt=\"\" width=\"190\" height=\"59\" \/>\r\n\r\nSince the band really begins at en as opposed to <em>Ec<\/em> like in the bulk the integral change from\r\n\r\n<\/div>\r\n<div>\r\n\r\n<img class=\"aligncenter size-full wp-image-138\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-73.png\" alt=\"\" width=\"487\" height=\"265\" \/>\r\n\r\n&nbsp;\r\n\r\n<strong>Density of states in the valance band<\/strong>\r\n\r\n&nbsp;\r\n\r\n<span style=\"text-align: initial;font-size: 1em\">As with the conduction band case we need the probability of occupying a given state in the valance band. This denoted \u210e(\u00a0 ) and is evaluated from<\/span>\r\n\r\n<\/div>\r\n<div><\/div>\r\n<div>\r\n\r\n<img class=\"aligncenter size-full wp-image-139\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-74.png\" alt=\"\" width=\"668\" height=\"326\" \/><img class=\"aligncenter size-full wp-image-140\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-75.png\" alt=\"\" width=\"437\" height=\"250\" \/>\r\n\r\n<strong>Fermi level position :2D<\/strong>\r\n\r\n&nbsp;\r\n\r\nThe procedure for finding the Fermi level position is the same as in the 3D Consider a spherical volume of\r\n\r\n&nbsp;\r\n\r\n<img class=\"aligncenter size-full wp-image-141\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-76.png\" alt=\"\" width=\"463\" height=\"407\" \/>\r\n\r\nNow the density is\r\n\r\n<\/div>\r\n<div>\r\n\r\n<img class=\"aligncenter size-full wp-image-142\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-77.png\" alt=\"\" width=\"156\" height=\"60\" \/>\r\n\r\nis the number of states per unit volume and the energy density is given as\r\n\r\n<img class=\"aligncenter size-full wp-image-143\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-78.png\" alt=\"\" width=\"217\" height=\"108\" \/>\r\n\r\n<span style=\"text-align: initial;font-size: 1em\">Divide by 2 to go back to only 1 spin orientation since in an optical transition spin slips are generally forbidden<\/span>\r\n\r\n<\/div>\r\n<div>\r\n\r\n<img class=\"aligncenter size-full wp-image-144\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-79.png\" alt=\"\" width=\"94\" height=\"52\" \/>\r\n\r\nThe expression applies to either conduction band or valance band. Applying the following equivalence (\u00a0 )\r\n\r\n<img class=\"aligncenter size-full wp-image-145\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-80.png\" alt=\"\" width=\"156\" height=\"121\" \/>\r\n<p style=\"text-align: justify\">where is the desired joint density of the states. Now from the conservation of momentum, transition in k are vertical such that the initial <em>k<\/em> value in the valance band is the same k value as in the conduction band (ka=kb=k) where ka is the k value in the valence band and kb is the value in the conduction band. The energy of the initial state in the valance band is<\/p>\r\n<img class=\"aligncenter size-full wp-image-146\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-81.png\" alt=\"\" width=\"140\" height=\"49\" \/>\r\n\r\n&nbsp;\r\n\r\nLikewise the energy of the final state in the conduction band is\r\n\r\n<img class=\"aligncenter size-full wp-image-147\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-82.png\" alt=\"\" width=\"477\" height=\"171\" \/>\r\n\r\n<\/div>\r\n<div>\r\n\r\n<img class=\"aligncenter size-full wp-image-148\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-83.png\" alt=\"\" width=\"572\" height=\"422\" \/>\r\n\r\nWhere for notational simplicity we have used the reduced mass\r\n\r\n<\/div>\r\n<div>\r\n\r\n<img class=\"aligncenter size-full wp-image-149\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-84.png\" alt=\"\" width=\"435\" height=\"308\" \/><img class=\"aligncenter size-full wp-image-150\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-85.png\" alt=\"\" width=\"199\" height=\"69\" \/>\r\n\r\n<strong>2D Well<\/strong>\r\n\r\n&nbsp;\r\n\r\nArea in k-space\r\n\r\n= ?<sub>?<\/sub> = 4??\r\n\r\n&nbsp;\r\n\r\nWhere the area occupied by a given mode or state is .Here we assume that represents the confined direction\r\n\r\n<img class=\"aligncenter size-full wp-image-151\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-86.png\" alt=\"\" width=\"77\" height=\"102\" \/>\r\n\r\nTogether, the number of modes in the area is\r\n\r\n<img class=\"aligncenter size-full wp-image-152\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-87.png\" alt=\"\" width=\"255\" height=\"55\" \/>\r\n\r\n<\/div>\r\n<div><span style=\"text-align: initial;font-size: 1em\">Multiply by 2 to account for spin<\/span><\/div>\r\n<div>\r\n\r\n<img class=\"aligncenter size-full wp-image-153\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-88.png\" alt=\"\" width=\"151\" height=\"61\" \/>\r\n\r\nNow consider the density\r\n\r\n<img class=\"aligncenter size-full wp-image-154\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-89.png\" alt=\"\" width=\"131\" height=\"56\" \/><span style=\"text-align: initial;font-size: 1em\">With the energy density given by<\/span><img class=\"aligncenter size-full wp-image-155\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-90.png\" alt=\"\" width=\"132\" height=\"93\" \/>\r\n\r\nStarting with the energy density\r\n\r\n<img class=\"aligncenter size-full wp-image-156\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-91.png\" alt=\"\" width=\"130\" height=\"44\" \/>\r\n\r\n&nbsp;\r\n\r\nDivide by 2 to get rid of the spin since formally speaking, spin flip optical transitions are forbidden\r\n\r\n<\/div>\r\n<div>\r\n\r\n<img class=\"aligncenter size-full wp-image-157\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-92.png\" alt=\"\" width=\"438\" height=\"239\" \/>\r\n<p style=\"text-align: justify\">wheree??(?) is the desired joint density of states. As before in the 3D case, the conservation of momentum means that transition in k-space are vertical. That is the initial k value in the valance band is the same as the final k value in the conduction band ( = = ) where (\u00a0 ) is the valance (conduction) band values.<\/p>\r\n&nbsp;\r\n\r\nThe energy of the initial state in the valance band is\r\n\r\n<img class=\"aligncenter size-full wp-image-158\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-93.png\" alt=\"\" width=\"137\" height=\"54\" \/>\r\n\r\nLikewise the energy of the final state in the conduction band is\r\n\r\n<\/div>\r\n<div>\r\n\r\n<img class=\"aligncenter size-full wp-image-159\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-94.png\" alt=\"\" width=\"459\" height=\"287\" \/>\r\n\r\n&nbsp;\r\n\r\nSuch that when replaced into our main expression the desired expression for the joint density of states is\r\n\r\n<img class=\"aligncenter size-full wp-image-160\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-95.png\" alt=\"\" width=\"95\" height=\"50\" \/>\r\n\r\n<strong>1D wire<\/strong>\r\n\r\nConsider the length in k-space\r\n\r\n&nbsp;\r\n\r\nL<sub>k<\/sub>=2<sub>k<\/sub>\r\n\r\n&nbsp;\r\n\r\nThe length occupied by a given mode or state is where\r\n\r\n<img class=\"aligncenter size-full wp-image-161\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-96.png\" alt=\"\" width=\"74\" height=\"48\" \/>\r\n\r\n<span style=\"font-size: 1em\">The number of states in the given length is<\/span>\r\n\r\n<\/div>\r\n<div>\r\n\r\n<img class=\"aligncenter size-full wp-image-162\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-97.png\" alt=\"\" width=\"163\" height=\"44\" \/>\r\n\r\nMultiply this by 2 to account for spin, we get total number of states as\r\n\r\n<img class=\"aligncenter size-full wp-image-163\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-98.png\" alt=\"\" width=\"136\" height=\"46\" \/>\r\n\r\nConsider the density ie number of states per unit length\r\n\r\n<img class=\"aligncenter size-full wp-image-164\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-99.png\" alt=\"\" width=\"107\" height=\"56\" \/>\r\n\r\nAnd the energy density is given by\r\n\r\n<img class=\"aligncenter size-full wp-image-165\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-100.png\" alt=\"\" width=\"181\" height=\"69\" \/>\r\n\r\n<span style=\"font-size: 1em;text-align: initial;text-indent: 1em\">Or alternately<\/span>\r\n\r\n<img class=\"aligncenter size-full wp-image-166\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-101.png\" alt=\"\" width=\"95\" height=\"56\" \/>\r\n\r\nStarting with the energy density\r\n\r\n<img class=\"aligncenter size-full wp-image-167\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-102.png\" alt=\"\" width=\"107\" height=\"65\" \/>\r\n\r\n<span style=\"text-align: initial;font-size: 1em\">Divide by 2 to consider only one spin orientation since spin flip transition are generally forbidden<\/span>\r\n\r\n<\/div>\r\n<div>\r\n\r\n<img class=\"aligncenter size-full wp-image-168\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-103.png\" alt=\"\" width=\"102\" height=\"48\" \/>\r\n\r\nNow apply the following equivalence\r\n\r\n<img class=\"aligncenter size-full wp-image-169\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-104.png\" alt=\"\" width=\"143\" height=\"90\" \/>\r\n<p style=\"text-align: justify\">wherep<sub>j<\/sub> (E) is the desired joint density of states. As before in the 3D and 2D case, the conservation of momentum means that transition in k-space are vertical so that K<sub>a<\/sub>=K<sub>b<\/sub>=K ) where k<sub>a<\/sub>(k<sub>b<\/sub>) is the valance (conduction) band values.<\/p>\r\n<img class=\"aligncenter size-full wp-image-170\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-105.png\" alt=\"\" width=\"165\" height=\"55\" \/>\r\n\r\nThe energy of the initial state in the valance band is\r\n\r\n<img class=\"aligncenter size-full wp-image-171\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-106.png\" alt=\"\" width=\"150\" height=\"49\" \/>\r\n\r\n<span style=\"text-align: initial;font-size: 1em\">Likewise the energy of the final state in the conduction band is<\/span>\r\n\r\n<img class=\"aligncenter size-full wp-image-172\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-107.png\" alt=\"\" width=\"481\" height=\"285\" \/>\r\n\r\n<span style=\"text-align: initial;font-size: 1em\">Such that when replaced into our main expression the desired expression for the joint density of states is<\/span>\r\n\r\n<\/div>\r\n<img class=\"aligncenter size-full wp-image-173\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-108.png\" alt=\"\" width=\"132\" height=\"60\" \/>\r\n\r\nNow to continue towards our final expression we express k fully. Since\r\n\r\n<img class=\"aligncenter size-full wp-image-174\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-109.png\" alt=\"\" width=\"139\" height=\"112\" \/>\r\n\r\nThis leads to the final expression for the joint density of states\r\n\r\n<img class=\"aligncenter size-full wp-image-175\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-110.png\" alt=\"\" width=\"214\" height=\"75\" \/>","rendered":"<div>\n<p>&nbsp;<\/p>\n<p>3.3.1\u00a0\u00a0\u00a0\u00a0 DOS in 3D<\/p>\n<p>3.3.2\u00a0\u00a0\u00a0\u00a0 DOS in 2D<\/p>\n<p>3.3.3\u00a0\u00a0\u00a0\u00a0 DOS in 1D<\/p>\n<p>3.3.4\u00a0\u00a0\u00a0 DOS in 0D<\/p>\n<\/div>\n<div>\n<p>&nbsp;<\/p>\n<p><strong>CALCULATION OF DENSITY OF STATES (DOS): Quantum Wells, Wires and Dots<\/strong><\/p>\n<p>&nbsp;<\/p>\n<p><strong style=\"font-size: 1em\">3.3.1 DOS for 3 dimensions (Bulk)<\/strong><\/p>\n<p>&nbsp;<\/p>\n<p><span style=\"text-align: initial;font-size: 1em\">Consider the volume in &#8220;k&#8221; space<\/span><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-107 aligncenter\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-42.png\" alt=\"\" width=\"76\" height=\"33\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-42.png 76w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-42-65x28.png 65w\" sizes=\"auto, (max-width: 76px) 100vw, 76px\" \/><\/p>\n<p>where for a particle in this space<\/p>\n<\/div>\n<div><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-108\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-43.png\" alt=\"\" width=\"235\" height=\"46\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-43.png 235w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-43-65x13.png 65w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-43-225x44.png 225w\" sizes=\"auto, (max-width: 235px) 100vw, 235px\" \/><\/div>\n<div>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-101\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-37.png\" alt=\"\" width=\"578\" height=\"374\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-37.png 578w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-37-300x194.png 300w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-37-65x42.png 65w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-37-225x146.png 225w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-37-350x226.png 350w\" sizes=\"auto, (max-width: 578px) 100vw, 578px\" \/><\/p>\n<p style=\"text-align: center\">Figure . Electron state is defined by a point in k-space.<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">Note that the 2 \u00a0arises from the constraints of periodic boundary conditions as proposed to the more general where <em>n<\/em>=0, 1, 2, 3&#8230; The volume of a given mode is then= . The number of modes (<em>N<\/em>) in the sphere is,<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-109\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-44.png\" alt=\"\" width=\"195\" height=\"46\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-44.png 195w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-44-65x15.png 65w\" sizes=\"auto, (max-width: 195px) 100vw, 195px\" \/><\/p>\n<p>Say the particle in an electron and we consider spin (up and down), then we multiply <em>N<\/em> by 2.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-110\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-45.png\" alt=\"\" width=\"220\" height=\"96\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-45.png 220w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-45-65x28.png 65w\" sizes=\"auto, (max-width: 220px) 100vw, 220px\" \/><\/p>\n<p>is the total number of states in sphere. Now consider the density<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-111\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-46.png\" alt=\"\" width=\"493\" height=\"304\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-46.png 493w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-46-300x185.png 300w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-46-65x40.png 65w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-46-225x139.png 225w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-46-350x216.png 350w\" sizes=\"auto, (max-width: 493px) 100vw, 493px\" \/><\/p>\n<p>&nbsp;<\/p>\n<\/div>\n<div>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-104\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-40.png\" alt=\"\" width=\"396\" height=\"195\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-40.png 396w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-40-300x148.png 300w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-40-65x32.png 65w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-40-225x111.png 225w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-40-350x172.png 350w\" sizes=\"auto, (max-width: 396px) 100vw, 396px\" \/><\/p>\n<p style=\"text-align: center\">Figure . Density of states in 3 dimension (Eq.3.48)<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<p><strong>3.3.2 DOS in Two Dimensions (well)<\/strong><\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">Here we have 1D that is quantized. Let&#8217;s us assume it is the z-direction. The total energy of this system is a sum of the energy along the quantized direction plus the energy along the other 2 free directions. It is expressed as<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-112\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-47.png\" alt=\"\" width=\"436\" height=\"100\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-47.png 436w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-47-300x69.png 300w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-47-65x15.png 65w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-47-225x52.png 225w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-47-350x80.png 350w\" sizes=\"auto, (max-width: 436px) 100vw, 436px\" \/><\/p>\n<p>&nbsp;<\/p>\n<p>where for the particle<\/p>\n<\/div>\n<div>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-113\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-48.png\" alt=\"\" width=\"74\" height=\"111\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-48.png 74w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-48-65x98.png 65w\" sizes=\"auto, (max-width: 74px) 100vw, 74px\" \/><\/p>\n<p>The area of a given mode is then ???? with the total number of modes (N) in the area being<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-114\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-49.png\" alt=\"\" width=\"185\" height=\"50\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-49.png 185w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-49-65x18.png 65w\" sizes=\"auto, (max-width: 185px) 100vw, 185px\" \/><\/p>\n<p>Again if the particle is an electron and we consider spin, multiply by 2 to get<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-115\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-50.png\" alt=\"\" width=\"183\" height=\"48\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-50.png 183w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-50-65x17.png 65w\" sizes=\"auto, (max-width: 183px) 100vw, 183px\" \/><\/p>\n<p style=\"text-align: justify\"><span style=\"text-align: initial;text-indent: 1em;font-size: 1em\">This is the energy density of the sub-band for a given or (<\/span><em style=\"text-align: initial;text-indent: 1em;font-size: 1em\">E<\/em><em style=\"text-align: initial;text-indent: 1em;font-size: 1em\">n<\/em><span style=\"text-align: initial;text-indent: 1em;font-size: 1em\">). For each successive there will be an additional \u045b2 and hence another subband. Therefore the density of the states is written<\/span><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-116\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-51.png\" alt=\"\" width=\"162\" height=\"40\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-51.png 162w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-51-65x16.png 65w\" sizes=\"auto, (max-width: 162px) 100vw, 162px\" \/><\/p>\n<p><span style=\"font-size: 1em;text-align: initial;text-indent: 1em\">Where \u0472 is the heavy side function.<\/span><\/p>\n<\/div>\n<div>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-117\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-52.png\" alt=\"\" width=\"294\" height=\"232\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-52.png 294w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-52-65x51.png 65w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-52-225x178.png 225w\" sizes=\"auto, (max-width: 294px) 100vw, 294px\" \/><\/p>\n<p style=\"text-align: center\"><span style=\"text-align: initial;font-size: 1em\">Figure Density of states in 2 dimension. Shaded area presents occupied states.<\/span><\/p>\n<\/div>\n<div>\n<p>&nbsp;<\/p>\n<p><strong>3.3.3 DOS in One Dimensions (Wire)<\/strong><\/p>\n<p>&nbsp;<\/p>\n<p>Consider now the situation where there are two dimensions confined and only 1 degree of freedom (say the x-direction). The total energy of the system can be written as<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-118\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-53.png\" alt=\"\" width=\"508\" height=\"117\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-53.png 508w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-53-300x69.png 300w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-53-65x15.png 65w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-53-225x52.png 225w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-53-350x81.png 350w\" sizes=\"auto, (max-width: 508px) 100vw, 508px\" \/><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-119\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-54.png\" alt=\"\" width=\"680\" height=\"115\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-54.png 680w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-54-300x51.png 300w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-54-65x11.png 65w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-54-225x38.png 225w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-54-350x59.png 350w\" sizes=\"auto, (max-width: 680px) 100vw, 680px\" \/><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-120\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-55.png\" alt=\"\" width=\"699\" height=\"377\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-55.png 699w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-55-300x162.png 300w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-55-65x35.png 65w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-55-225x121.png 225w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-55-350x189.png 350w\" sizes=\"auto, (max-width: 699px) 100vw, 699px\" \/><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-121\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-56.png\" alt=\"\" width=\"295\" height=\"190\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-56.png 295w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-56-65x42.png 65w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-56-225x145.png 225w\" sizes=\"auto, (max-width: 295px) 100vw, 295px\" \/><\/p>\n<\/div>\n<div>\n<p style=\"text-align: center\">Figure Density of states in 1 dimension. Shaded area presents occupied states.<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<p><strong>3.3.4 Zero dimensions (Quantum Dot)<\/strong><\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">Here since all three dimensions are confined. The density of states is basically a series of delta functions. The total energy of the system is<\/p>\n<\/div>\n<div>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-122\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-57.png\" alt=\"\" width=\"649\" height=\"215\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-57.png 649w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-57-300x99.png 300w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-57-65x22.png 65w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-57-225x75.png 225w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-57-350x116.png 350w\" sizes=\"auto, (max-width: 649px) 100vw, 649px\" \/><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-123\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-58.png\" alt=\"\" width=\"578\" height=\"247\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-58.png 578w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-58-300x128.png 300w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-58-65x28.png 65w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-58-225x96.png 225w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-58-350x150.png 350w\" sizes=\"auto, (max-width: 578px) 100vw, 578px\" \/><\/p>\n<p>&nbsp;<\/p>\n<p><strong>3.3.5 More density of states<\/strong><\/p>\n<p>&nbsp;<\/p>\n<p><strong>Density of states in the conduction band<\/strong><\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">For this we need to know the probability that an electron will occupy a given stats of energy E. The Probability, P(E), is referred as the Fermi Dirac distribution. In addition we need to know the density of states ( \u2032). The density of states has units of number of unit volume per unit energy. Therefore \u2032 is the number of states per unit volume. The number of occupied states at a given energy per unit volume is therefore<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-124\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-59.png\" alt=\"\" width=\"186\" height=\"34\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-59.png 186w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-59-65x12.png 65w\" sizes=\"auto, (max-width: 186px) 100vw, 186px\" \/><\/p>\n<p>Here\u00a0 \u00a0is the Fermi energy.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-125\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-60.png\" alt=\"\" width=\"141\" height=\"50\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-60.png 141w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-60-65x23.png 65w\" sizes=\"auto, (max-width: 141px) 100vw, 141px\" \/><\/p>\n<p>the total concentration of electrons in the conduction band is therefore the integral over all available energies<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-126\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-61.png\" alt=\"\" width=\"182\" height=\"38\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-61.png 182w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-61-65x14.png 65w\" sizes=\"auto, (max-width: 182px) 100vw, 182px\" \/><\/p>\n<p>where?<sub>c<\/sub> is the energy where conduction band starts. For the case of three dimensional material<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-127\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-62.png\" alt=\"\" width=\"160\" height=\"42\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-62.png 160w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-62-65x17.png 65w\" sizes=\"auto, (max-width: 160px) 100vw, 160px\" \/><\/p>\n<p>Taking account into conduction band begins, the density of states can be written as<\/p>\n<p>&nbsp;<\/p>\n<\/div>\n<div>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-128\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-63.png\" alt=\"\" width=\"627\" height=\"116\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-63.png 627w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-63-300x56.png 300w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-63-65x12.png 65w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-63-225x42.png 225w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-63-350x65.png 350w\" sizes=\"auto, (max-width: 627px) 100vw, 627px\" \/><\/p>\n<p>The integral is called the Fermi integral or Fermi Dirac integral.<\/p>\n<p>&nbsp;<\/p>\n<p>Consider the case where, E\u00a0 \u2212 E<sub>r\u00a0<\/sub>\u226b KTand the Fermi Dirac distribution function becomes<\/p>\n<\/div>\n<div><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-129\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-64.png\" alt=\"\" width=\"640\" height=\"483\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-64.png 640w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-64-300x226.png 300w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-64-65x49.png 65w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-64-225x170.png 225w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-64-350x264.png 350w\" sizes=\"auto, (max-width: 640px) 100vw, 640px\" \/><\/div>\n<div>\n<p>&nbsp;<\/p>\n<p><strong><em>This is the expression for the effective density of states of the conduction band.<\/em><\/strong><\/p>\n<p>&nbsp;<\/p>\n<p><strong>Density of states in the valance band<\/strong><\/p>\n<p>&nbsp;<\/p>\n<p>The number of holes at a given energy per unit volume is given as<\/p>\n<\/div>\n<div><\/div>\n<div>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-130\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-65.png\" alt=\"\" width=\"524\" height=\"231\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-65.png 524w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-65-300x132.png 300w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-65-65x29.png 65w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-65-225x99.png 225w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-65-350x154.png 350w\" sizes=\"auto, (max-width: 524px) 100vw, 524px\" \/><\/p>\n<p style=\"text-align: justify\">Where Ev is the energy where valance band starts. The total concentration of holes in the valance band is the integral over all energies.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-131\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-66.png\" alt=\"\" width=\"657\" height=\"499\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-66.png 657w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-66-300x228.png 300w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-66-65x49.png 65w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-66-225x171.png 225w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-66-350x266.png 350w\" sizes=\"auto, (max-width: 657px) 100vw, 657px\" \/><\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\"><span style=\"font-size: 1em;text-align: initial\">This is the effective density of the states in the valance band.<\/span><\/p>\n<\/div>\n<div>\n<p>&nbsp;<\/p>\n<p><strong>Summary<\/strong><\/p>\n<p>&nbsp;<\/p>\n<p style=\"text-align: justify\">Fermi level of an intrinsic semiconductor\u00a0 If the bulk semiconductor is intrinsic, there has been no doping of the material and hence no extra electrons or holes anywhere. in this situation<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-132\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-67.png\" alt=\"\" width=\"464\" height=\"192\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-67.png 464w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-67-300x124.png 300w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-67-65x27.png 65w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-67-225x93.png 225w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-67-350x145.png 350w\" sizes=\"auto, (max-width: 464px) 100vw, 464px\" \/><\/p>\n<p style=\"text-align: justify\"><strong><em>One can therefore see that at T=0 the Fermi energy of an intrinsic semiconductor is at the halfway point between the top of the valance band and the bottom of the conduction band.<\/em><\/strong><\/p>\n<p>&nbsp;<\/p>\n<p><strong>Density of states in the conduction band<\/strong><\/p>\n<p>&nbsp;<\/p>\n<p>We start with the Fermi Dirac distribution for electrons and also the density of states<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-133\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-68.png\" alt=\"\" width=\"174\" height=\"35\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-68.png 174w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-68-65x13.png 65w\" sizes=\"auto, (max-width: 174px) 100vw, 174px\" \/>Consider only one of the subband. In this case the density of states simplifies to<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-134\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-69.png\" alt=\"\" width=\"98\" height=\"36\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-69.png 98w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-69-65x24.png 65w\" sizes=\"auto, (max-width: 98px) 100vw, 98px\" \/><\/p>\n<\/div>\n<div>\n<p><span style=\"text-align: initial;font-size: 1em\">Now recall from the previous section that the number of states at a given energy per unit volume<\/span><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-135\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-70.png\" alt=\"\" width=\"194\" height=\"26\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-70.png 194w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-70-65x9.png 65w\" sizes=\"auto, (max-width: 194px) 100vw, 194px\" \/><\/p>\n<p style=\"text-align: justify\">the total concentration of electrons in this first subband is the integral over all available energies. Rather than use ntot as before let&#8217;s just stick to <em>n<\/em><em>c<\/em> from the start<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-136\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-71.png\" alt=\"\" width=\"495\" height=\"91\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-71.png 495w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-71-300x55.png 300w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-71-65x12.png 65w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-71-225x41.png 225w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-71-350x64.png 350w\" sizes=\"auto, (max-width: 495px) 100vw, 495px\" \/><\/p>\n<\/div>\n<div>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-137\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-72.png\" alt=\"\" width=\"190\" height=\"59\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-72.png 190w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-72-65x20.png 65w\" sizes=\"auto, (max-width: 190px) 100vw, 190px\" \/><\/p>\n<p>Since the band really begins at en as opposed to <em>Ec<\/em> like in the bulk the integral change from<\/p>\n<\/div>\n<div>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-138\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-73.png\" alt=\"\" width=\"487\" height=\"265\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-73.png 487w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-73-300x163.png 300w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-73-65x35.png 65w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-73-225x122.png 225w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-73-350x190.png 350w\" sizes=\"auto, (max-width: 487px) 100vw, 487px\" \/><\/p>\n<p>&nbsp;<\/p>\n<p><strong>Density of states in the valance band<\/strong><\/p>\n<p>&nbsp;<\/p>\n<p><span style=\"text-align: initial;font-size: 1em\">As with the conduction band case we need the probability of occupying a given state in the valance band. This denoted \u210e(\u00a0 ) and is evaluated from<\/span><\/p>\n<\/div>\n<div><\/div>\n<div>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-139\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-74.png\" alt=\"\" width=\"668\" height=\"326\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-74.png 668w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-74-300x146.png 300w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-74-65x32.png 65w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-74-225x110.png 225w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-74-350x171.png 350w\" sizes=\"auto, (max-width: 668px) 100vw, 668px\" \/><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-140\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-75.png\" alt=\"\" width=\"437\" height=\"250\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-75.png 437w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-75-300x172.png 300w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-75-65x37.png 65w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-75-225x129.png 225w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-75-350x200.png 350w\" sizes=\"auto, (max-width: 437px) 100vw, 437px\" \/><\/p>\n<p><strong>Fermi level position :2D<\/strong><\/p>\n<p>&nbsp;<\/p>\n<p>The procedure for finding the Fermi level position is the same as in the 3D Consider a spherical volume of<\/p>\n<p>&nbsp;<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-141\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-76.png\" alt=\"\" width=\"463\" height=\"407\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-76.png 463w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-76-300x264.png 300w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-76-65x57.png 65w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-76-225x198.png 225w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-76-350x308.png 350w\" sizes=\"auto, (max-width: 463px) 100vw, 463px\" \/><\/p>\n<p>Now the density is<\/p>\n<\/div>\n<div>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-142\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-77.png\" alt=\"\" width=\"156\" height=\"60\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-77.png 156w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-77-65x25.png 65w\" sizes=\"auto, (max-width: 156px) 100vw, 156px\" \/><\/p>\n<p>is the number of states per unit volume and the energy density is given as<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-143\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-78.png\" alt=\"\" width=\"217\" height=\"108\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-78.png 217w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-78-65x32.png 65w\" sizes=\"auto, (max-width: 217px) 100vw, 217px\" \/><\/p>\n<p><span style=\"text-align: initial;font-size: 1em\">Divide by 2 to go back to only 1 spin orientation since in an optical transition spin slips are generally forbidden<\/span><\/p>\n<\/div>\n<div>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-144\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-79.png\" alt=\"\" width=\"94\" height=\"52\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-79.png 94w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-79-65x36.png 65w\" sizes=\"auto, (max-width: 94px) 100vw, 94px\" \/><\/p>\n<p>The expression applies to either conduction band or valance band. Applying the following equivalence (\u00a0 )<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-145\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-80.png\" alt=\"\" width=\"156\" height=\"121\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-80.png 156w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-80-65x50.png 65w\" sizes=\"auto, (max-width: 156px) 100vw, 156px\" \/><\/p>\n<p style=\"text-align: justify\">where is the desired joint density of the states. Now from the conservation of momentum, transition in k are vertical such that the initial <em>k<\/em> value in the valance band is the same k value as in the conduction band (ka=kb=k) where ka is the k value in the valence band and kb is the value in the conduction band. The energy of the initial state in the valance band is<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-146\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-81.png\" alt=\"\" width=\"140\" height=\"49\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-81.png 140w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-81-65x23.png 65w\" sizes=\"auto, (max-width: 140px) 100vw, 140px\" \/><\/p>\n<p>&nbsp;<\/p>\n<p>Likewise the energy of the final state in the conduction band is<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-147\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-82.png\" alt=\"\" width=\"477\" height=\"171\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-82.png 477w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-82-300x108.png 300w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-82-65x23.png 65w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-82-225x81.png 225w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-82-350x125.png 350w\" sizes=\"auto, (max-width: 477px) 100vw, 477px\" \/><\/p>\n<\/div>\n<div>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-148\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-83.png\" alt=\"\" width=\"572\" height=\"422\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-83.png 572w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-83-300x221.png 300w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-83-65x48.png 65w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-83-225x166.png 225w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-83-350x258.png 350w\" sizes=\"auto, (max-width: 572px) 100vw, 572px\" \/><\/p>\n<p>Where for notational simplicity we have used the reduced mass<\/p>\n<\/div>\n<div>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-149\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-84.png\" alt=\"\" width=\"435\" height=\"308\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-84.png 435w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-84-300x212.png 300w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-84-65x46.png 65w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-84-225x159.png 225w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-84-350x248.png 350w\" sizes=\"auto, (max-width: 435px) 100vw, 435px\" \/><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-150\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-85.png\" alt=\"\" width=\"199\" height=\"69\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-85.png 199w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-85-65x23.png 65w\" sizes=\"auto, (max-width: 199px) 100vw, 199px\" \/><\/p>\n<p><strong>2D Well<\/strong><\/p>\n<p>&nbsp;<\/p>\n<p>Area in k-space<\/p>\n<p>= ?<sub>?<\/sub> = 4??<\/p>\n<p>&nbsp;<\/p>\n<p>Where the area occupied by a given mode or state is .Here we assume that represents the confined direction<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-151\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-86.png\" alt=\"\" width=\"77\" height=\"102\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-86.png 77w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-86-65x86.png 65w\" sizes=\"auto, (max-width: 77px) 100vw, 77px\" \/><\/p>\n<p>Together, the number of modes in the area is<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-152\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-87.png\" alt=\"\" width=\"255\" height=\"55\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-87.png 255w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-87-65x14.png 65w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-87-225x49.png 225w\" sizes=\"auto, (max-width: 255px) 100vw, 255px\" \/><\/p>\n<\/div>\n<div><span style=\"text-align: initial;font-size: 1em\">Multiply by 2 to account for spin<\/span><\/div>\n<div>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-153\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-88.png\" alt=\"\" width=\"151\" height=\"61\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-88.png 151w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-88-150x61.png 150w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-88-65x26.png 65w\" sizes=\"auto, (max-width: 151px) 100vw, 151px\" \/><\/p>\n<p>Now consider the density<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-154\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-89.png\" alt=\"\" width=\"131\" height=\"56\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-89.png 131w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-89-65x28.png 65w\" sizes=\"auto, (max-width: 131px) 100vw, 131px\" \/><span style=\"text-align: initial;font-size: 1em\">With the energy density given by<\/span><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-155\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-90.png\" alt=\"\" width=\"132\" height=\"93\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-90.png 132w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-90-65x46.png 65w\" sizes=\"auto, (max-width: 132px) 100vw, 132px\" \/><\/p>\n<p>Starting with the energy density<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-156\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-91.png\" alt=\"\" width=\"130\" height=\"44\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-91.png 130w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-91-65x22.png 65w\" sizes=\"auto, (max-width: 130px) 100vw, 130px\" \/><\/p>\n<p>&nbsp;<\/p>\n<p>Divide by 2 to get rid of the spin since formally speaking, spin flip optical transitions are forbidden<\/p>\n<\/div>\n<div>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-157\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-92.png\" alt=\"\" width=\"438\" height=\"239\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-92.png 438w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-92-300x164.png 300w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-92-65x35.png 65w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-92-225x123.png 225w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-92-350x191.png 350w\" sizes=\"auto, (max-width: 438px) 100vw, 438px\" \/><\/p>\n<p style=\"text-align: justify\">wheree??(?) is the desired joint density of states. As before in the 3D case, the conservation of momentum means that transition in k-space are vertical. That is the initial k value in the valance band is the same as the final k value in the conduction band ( = = ) where (\u00a0 ) is the valance (conduction) band values.<\/p>\n<p>&nbsp;<\/p>\n<p>The energy of the initial state in the valance band is<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-158\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-93.png\" alt=\"\" width=\"137\" height=\"54\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-93.png 137w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-93-65x26.png 65w\" sizes=\"auto, (max-width: 137px) 100vw, 137px\" \/><\/p>\n<p>Likewise the energy of the final state in the conduction band is<\/p>\n<\/div>\n<div>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-159\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-94.png\" alt=\"\" width=\"459\" height=\"287\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-94.png 459w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-94-300x188.png 300w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-94-65x41.png 65w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-94-225x141.png 225w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-94-350x219.png 350w\" sizes=\"auto, (max-width: 459px) 100vw, 459px\" \/><\/p>\n<p>&nbsp;<\/p>\n<p>Such that when replaced into our main expression the desired expression for the joint density of states is<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-160\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-95.png\" alt=\"\" width=\"95\" height=\"50\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-95.png 95w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-95-65x34.png 65w\" sizes=\"auto, (max-width: 95px) 100vw, 95px\" \/><\/p>\n<p><strong>1D wire<\/strong><\/p>\n<p>Consider the length in k-space<\/p>\n<p>&nbsp;<\/p>\n<p>L<sub>k<\/sub>=2<sub>k<\/sub><\/p>\n<p>&nbsp;<\/p>\n<p>The length occupied by a given mode or state is where<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-161\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-96.png\" alt=\"\" width=\"74\" height=\"48\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-96.png 74w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-96-65x42.png 65w\" sizes=\"auto, (max-width: 74px) 100vw, 74px\" \/><\/p>\n<p><span style=\"font-size: 1em\">The number of states in the given length is<\/span><\/p>\n<\/div>\n<div>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-162\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-97.png\" alt=\"\" width=\"163\" height=\"44\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-97.png 163w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-97-65x18.png 65w\" sizes=\"auto, (max-width: 163px) 100vw, 163px\" \/><\/p>\n<p>Multiply this by 2 to account for spin, we get total number of states as<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-163\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-98.png\" alt=\"\" width=\"136\" height=\"46\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-98.png 136w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-98-65x22.png 65w\" sizes=\"auto, (max-width: 136px) 100vw, 136px\" \/><\/p>\n<p>Consider the density ie number of states per unit length<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-164\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-99.png\" alt=\"\" width=\"107\" height=\"56\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-99.png 107w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-99-65x34.png 65w\" sizes=\"auto, (max-width: 107px) 100vw, 107px\" \/><\/p>\n<p>And the energy density is given by<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-165\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-100.png\" alt=\"\" width=\"181\" height=\"69\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-100.png 181w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-100-65x25.png 65w\" sizes=\"auto, (max-width: 181px) 100vw, 181px\" \/><\/p>\n<p><span style=\"font-size: 1em;text-align: initial;text-indent: 1em\">Or alternately<\/span><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-166\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-101.png\" alt=\"\" width=\"95\" height=\"56\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-101.png 95w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-101-65x38.png 65w\" sizes=\"auto, (max-width: 95px) 100vw, 95px\" \/><\/p>\n<p>Starting with the energy density<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-167\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-102.png\" alt=\"\" width=\"107\" height=\"65\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-102.png 107w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-102-65x39.png 65w\" sizes=\"auto, (max-width: 107px) 100vw, 107px\" \/><\/p>\n<p><span style=\"text-align: initial;font-size: 1em\">Divide by 2 to consider only one spin orientation since spin flip transition are generally forbidden<\/span><\/p>\n<\/div>\n<div>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-168\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-103.png\" alt=\"\" width=\"102\" height=\"48\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-103.png 102w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-103-65x31.png 65w\" sizes=\"auto, (max-width: 102px) 100vw, 102px\" \/><\/p>\n<p>Now apply the following equivalence<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-169\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-104.png\" alt=\"\" width=\"143\" height=\"90\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-104.png 143w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-104-65x41.png 65w\" sizes=\"auto, (max-width: 143px) 100vw, 143px\" \/><\/p>\n<p style=\"text-align: justify\">wherep<sub>j<\/sub> (E) is the desired joint density of states. As before in the 3D and 2D case, the conservation of momentum means that transition in k-space are vertical so that K<sub>a<\/sub>=K<sub>b<\/sub>=K ) where k<sub>a<\/sub>(k<sub>b<\/sub>) is the valance (conduction) band values.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-170\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-105.png\" alt=\"\" width=\"165\" height=\"55\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-105.png 165w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-105-65x22.png 65w\" sizes=\"auto, (max-width: 165px) 100vw, 165px\" \/><\/p>\n<p>The energy of the initial state in the valance band is<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-171\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-106.png\" alt=\"\" width=\"150\" height=\"49\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-106.png 150w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-106-65x21.png 65w\" sizes=\"auto, (max-width: 150px) 100vw, 150px\" \/><\/p>\n<p><span style=\"text-align: initial;font-size: 1em\">Likewise the energy of the final state in the conduction band is<\/span><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-172\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-107.png\" alt=\"\" width=\"481\" height=\"285\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-107.png 481w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-107-300x178.png 300w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-107-65x39.png 65w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-107-225x133.png 225w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-107-350x207.png 350w\" sizes=\"auto, (max-width: 481px) 100vw, 481px\" \/><\/p>\n<p><span style=\"text-align: initial;font-size: 1em\">Such that when replaced into our main expression the desired expression for the joint density of states is<\/span><\/p>\n<\/div>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-173\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-108.png\" alt=\"\" width=\"132\" height=\"60\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-108.png 132w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-108-65x30.png 65w\" sizes=\"auto, (max-width: 132px) 100vw, 132px\" \/><\/p>\n<p>Now to continue towards our final expression we express k fully. Since<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-174\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-109.png\" alt=\"\" width=\"139\" height=\"112\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-109.png 139w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-109-65x52.png 65w\" sizes=\"auto, (max-width: 139px) 100vw, 139px\" \/><\/p>\n<p>This leads to the final expression for the joint density of states<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-175\" src=\"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/wp-content\/uploads\/sites\/96\/2018\/11\/2-110.png\" alt=\"\" width=\"214\" height=\"75\" srcset=\"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-110.png 214w, https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-content\/uploads\/sites\/96\/2018\/11\/2-110-65x23.png 65w\" sizes=\"auto, (max-width: 214px) 100vw, 214px\" \/><\/p>\n","protected":false},"author":3,"menu_order":8,"template":"","meta":{"_acf_changed":false,"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-98","chapter","type-chapter","status-publish","hentry"],"part":3,"_links":{"self":[{"href":"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-json\/pressbooks\/v2\/chapters\/98","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-json\/wp\/v2\/users\/3"}],"version-history":[{"count":5,"href":"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-json\/pressbooks\/v2\/chapters\/98\/revisions"}],"predecessor-version":[{"id":177,"href":"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-json\/pressbooks\/v2\/chapters\/98\/revisions\/177"}],"part":[{"href":"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-json\/pressbooks\/v2\/parts\/3"}],"metadata":[{"href":"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-json\/pressbooks\/v2\/chapters\/98\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-json\/wp\/v2\/media?parent=98"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-json\/pressbooks\/v2\/chapter-type?post=98"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-json\/wp\/v2\/contributor?post=98"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/ebooks.inflibnet.ac.in\/phy12\/wp-json\/wp\/v2\/license?post=98"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}