Introduction to the Quantum Theory of Solids3.pdf

《Introduction to the Quantum Theory of Solids3.pdf》由会员上传分享，免费在线阅读，更多相关内容在学术论文-天天文库。

1、Chapter3IntroductiontotheQuantumTheoryofSolids3.2ElectricalConductioninSolids3.2.1TheEnergyBandandtheBondModelTwo-dimensionalrepresentationofthecovalentbondinginasemiconductorofSiatT=0K.原子二度空間表示圖，0K時的狀況。1s11s2Siliconatomhas14electronsSilicon(Si)atomEnergystateQuantumstaten=11s1,1s

2、2Fullfilledn=22s1,2s2Fullfilledn=22p1,2p2,2p3,2p4,2p5,2p6,Fullfilledn=33s1,3s2,3p1,3p2Partialfilled形成共價鍵的電子都在價帶covalentbond(valenceband)脫離共價鍵的電子就跑到導帶Breakbond(conductionband)Asthetemperatureincreaseabove0K,afewvalencebandelectronsmaygainenoughthermalenergytobreakthecovalentbondand

3、jumpintotheconductionband.當溫度逐漸上升高於0k時，價帶電子從環境的熱中獲得能量，進而躍遷到導帶。Thesemiconductorisnearlyneutrallycharged.Thismeansthat,asthenegativelychargedelectronbreaksawayfromitscovalentbondingposition,apositivelycharged“emptystate”iscreatedintheoriginalcovalentbondingpositioninthevalenceband.材

4、料原本是電中性，一個帶負電的電子(在導帶)脫離原子核(在價帶)，並且在原位置留下一個帶正電的空缺。表示法一表示法二Ey能階示意圖x空間示意圖xTwo-dimensionalrepresentationofCorrespondinglinerepresentationofthebreakingofacovalentbond.theenergybandandgenerationofanegativeandpositivechargewiththeFigure13breakingofacovalentbond.表示法三能階示意圖能階示意圖TheEversuskd

5、iagramofaconductionandvalencebandofasemiconductorat(a)T=0Kand(b)T>0K.3.2.2Driftcurrent(飄移電流)IfwehaveacollectionofpositivelychargedionswithavolumedensityN(cm-3)andanaveragedriftvelocity(cm/s),thenthedriftcurrentwoulddbe假如我們考慮一群正電荷離子的平均行為則，飄移電流密度JJNqN載體數量密度(#/m3)d載體電荷之電量大小(？庫輪)

6、d平均飄移速率If,insteadofconsideringtheaveragedriftvelocity,weconsideredtheindividualionvelocities,thenwecouldwritethedriftcurrentdensityas取而代之的，如果不考慮平均行為，而是考慮個別的行為，則飄移電流密度JNJqii13.2.3Electroneffectivemass(電子等效質量)電子的加速度Infreespace電子靜止質量Fm,aFqEextoextEelectricfieldext電子帶負電

7、因此電子沿著反電場方向移動。InGaAsEelectricfieldextFm,aFqEextext摩擦力在GaAs材料內移動，電子感受摩擦力m=100kgo500Nta=5m/sec2冰：沒有摩擦力F500Ntext2m=100kgFma250kg2sec/moextm*=250kg500Nta=2m/sec2泥巴地：有摩擦力F500Ntext2Fma100kg5sec/mexto3.2.3Electroneffectivemass(電子等效質量)Themovementofanelectr

8、oninalatticewill,ingeneral,bediff