{"id":473,"date":"2018-11-19T05:35:34","date_gmt":"2018-11-19T05:35:34","guid":{"rendered":"http:\/\/phy12.epgpbooks.inflibnet.ac.in\/?post_type=chapter&p=473"},"modified":"2019-04-30T11:05:39","modified_gmt":"2019-04-30T11:05:39","slug":"semiconductor-band-structure","status":"publish","type":"chapter","link":"https:\/\/ebooks.inflibnet.ac.in\/phy12\/chapter\/semiconductor-band-structure\/","title":{"rendered":"Semiconductor Nanoparticle"},"content":{"raw":"
\"epgp<\/a>\r\n<\/span><\/div>\r\n
\r\n\r\n \r\n\r\n \r\n\r\n \r\n

In semiconductors we are interested in the valence band and conduction band. Moreover, for most applications we are interested in what happens near the top of the valence band and the bottom of the conduction band. These states originate from the atomic levels of the valence shell in the elements making up the semiconductor.<\/p>\r\n \r\n\r\nIV Semiconductors<\/strong>\r\n\r\n \r\n\r\nC 1s2<\/sup> 2s2<\/sup> 2p2<\/sup>\r\n\r\nSi 1s2<\/sup> 2s2<\/sup> 2p6<\/sup> 3s2<\/sup> 3p2<\/sup>\r\n\r\nGe 1s2<\/sup> 2s2<\/sup> 2p6<\/sup> 3s2<\/sup> 3p6<\/sup> 3d10<\/sup> 4s2<\/sup> 4p2<\/sup>\r\n\r\n \r\n\r\nIII-V Semiconductors<\/strong>\r\n\r\n \r\n\r\nGa 1s2<\/sup> 2s2<\/sup> 2p6<\/sup> 3s2<\/sup> 3p6<\/sup> 3d10<\/sup> 4s2<\/sup> 4p1<\/sup><\/span>\r\n\r\nIn 1s2<\/sup> 2s2<\/sup> 2p6<\/sup> 3s2<\/sup> 3p6<\/sup> 3d10<\/sup> 4s2<\/sup> 4p6<\/sup> 4d10<\/sup> 5s2<\/sup> 5p1<\/sup>\r\n\r\nAs 1s2<\/sup> 2s2<\/sup> 2p6<\/sup> 3s2<\/sup> 3p6<\/sup> 3d10<\/sup> 4s2<\/sup> 4p3<\/sup>\r\n\r\nP 1s2<\/sup> 2s2<\/sup> 2p6<\/sup> 3s2<\/sup> 3p3<\/sup>\r\n\r\n \r\n\r\nII-VI Semiconductors<\/strong>\r\n\r\n \r\n\r\nCd 1s2<\/sup> 2s2<\/sup> 2p6<\/sup> 3s2<\/sup> 3p6<\/sup> 3d10<\/sup> 4s2<\/sup> 4p6<\/sup> 4d10<\/sup> 5s2<\/sup>\r\n\r\nZn 1s2<\/sup> 2s2<\/sup> 2p6<\/sup> 3s2<\/sup> 3p6<\/sup> 3d10<\/sup> 4s2<\/sup>\r\n\r\nS 1s2<\/sup> 2s2<\/sup> 2p6<\/sup> 3s2<\/sup> 3p4 <\/sup>\r\n\r\nSe 1s2<\/sup> 2s2<\/sup> 2p6<\/sup> 3s2<\/sup> 3p6<\/sup> 3d10<\/sup> 4s2<\/sup> 4p4 <\/sup>\r\n\r\nTe 1s2<\/sup> 2s2<\/sup> 2p6<\/sup> 3s2<\/sup> 3p6<\/sup> 3d10<\/sup> 4s2<\/sup> 4p6<\/sup> 4d10<\/sup> 5s2<\/sup> 5p4<\/sup>\r\n\r\n<\/div>\r\n

<\/div>\r\n \r\n\r\nBand structure: CdSe<\/strong>\r\n\r\n \r\n

The dash line represents the Fermi level (EF) at - 4.0427 eV, LCB and HVB are the lowest conduction and the highest valence bands, respectively. The band structure of hexagonal CdSe (c), Z(001), M(110) are the Brillouin-zone boundary points.<\/span><\/p>\r\n\"\"\r\n

CdSe band structure along major direction (\u0393Z lines in Brillouin zone) is corresponding band dispersion (along \u0393M and \u0393Z direction).<\/span><\/p>\r\n \r\n

(a) The Brillouin zone for 3D zinc-blende structure and its 2D projection. (b) Comparison of the band structures of CdSe NP (black lines) and bulk CdSe (red lines).<\/span><\/p>\r\n\r\n

\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n
Parameter<\/td>\r\nCdSe<\/td>\r\n<\/tr>\r\n
Spin\u00a0 orbit\u00a0splitting\u00a0(eV)<\/td>\r\n0.39<\/td>\r\n<\/tr>\r\n
Lattice\u00a0constant\u00a0(nm)<\/td>\r\n0.61<\/td>\r\n<\/tr>\r\n
me (m0)<\/td>\r\n0.18<\/td>\r\n<\/tr>\r\n
mhh (m0)<\/td>\r\n0.89<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<\/div>\r\n
<\/div>\r\n \r\n\r\nBand Structure: Silicon<\/strong>\r\n\r\n \r\n

Although the band structure of Si is far from ideal, having an indirect band gap, hig hole masses, and small spin-orbit splitting, processing related advantages make Si the premier semiconductor for consumer electronics. On the right we show constant energy ellipsoids for Si conduction band. There are six equivalent valleys in Si at the band edge.<\/span><\/p>\r\n\r\n

\r\n\r\n\"\"\r\n\r\nIndirect gap material\u00a0 weak optical transitions, can\u2019t be used to produce lasers.\r\n\r\n \r\n\r\n\"\"\r\n\r\n<\/div>\r\n
\r\n\r\n \r\n\r\nBand Structure: GaAs<\/strong>\r\n\r\n \r\n

The bandgap at 0K is 1.51 eV and at 300 K it is 1.43 eV. The bottom of the conduction band is at k = (0, 0, 0), i.e., the G-point. The upper conduction band valleys are at the L-point.<\/span><\/p>\r\n\r\n<\/div>\r\n

\r\n\r\n\"\"\r\n\r\nConduction band:<\/strong>\r\n\r\n \r\n\r\n-\u00a0 Electron mass is light.\u00a0 m* = 0.067 m0\r\n\r\n-\u00a0 Upper valley mass is large. m* = 0.25 m0 results in negative differential resistance at higher fields.\r\n\r\n-\u00a0\u00a0 Material is direct bandgap and has strong optical transitions can be used for light emission\r\n\r\n \r\n\r\nValence band:<\/strong>\r\n