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1、第七章第七章 金属和半金属和半导体的接触导体的接触Contact between Metal and Contact between Metal and SemiconductorSemiconductor7.1 金属金属-半导体接触和能级图半导体接触和能级图Contact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramCo
2、ntact between Metal and Semiconductor and Band Diagram7.1.1 金属和半导体的功函数EcEvWmWsEFmEFsE0EnContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and
3、Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band Diagram7.1.2 接触电势差 Contact between Metal and Semiconductor and Band Dia
4、gramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between
5、Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band Diagram金属和半导体的电势接触电势差若金属与半导体间距减小，接触电势差一部分落在空间电荷区，一部分降落在金属和半导体表面之间：若紧密接触，则Vms很小，接触电势差大部分落在空间电荷区。金属与半导体之间距离远大于原子间距忽略忽略忽略忽略间间隙中隙中隙中隙中电势电势差，差，差，差，导带底电子向金属运动时必须越过的势垒的高导带底电子向金属运动时必须越过的势垒的高导带底电子向金属运动时必须越过的势垒的高导带底电子向金属运
6、动时必须越过的势垒的高度：度：度：度：qVD=-qVs=Wm-Ws （1）金属一边的电子运动到半导体一边也需要越过的势垒高度：金属一边的电子运动到半导体一边也需要越过的势垒高度：金属一边的电子运动到半导体一边也需要越过的势垒高度：金属一边的电子运动到半导体一边也需要越过的势垒高度：qVDEcEFEvContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconducto
7、r and Band DiagramContact between Metal and Semiconductor and Band Diagram阻挡层与反阻挡层阻挡层与反阻挡层 Contact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor a
8、nd Band Diagram（1）金属）金属-n型半导体接触型半导体接触Contact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band Diagram（a）WmWs 电子阻挡层电子阻挡层电子阻挡层电子阻挡层:Contact be
9、tween Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semi
10、conductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band Diagram金属一边的势垒金属一边的势垒 半导体一边的势垒半导体一边的势垒 Contact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Me
11、tal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band Diagram（b）WmWm 空穴阻挡层空穴阻挡层:EFmEFsWsWmEvEcE0Contact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramCon
12、tact between Metal and Semiconductor and Band Diagram接触后：接触后：qVD=Ws-Wm xDEFEvEcContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band Diag
13、ram（2）WmWs 空穴反阻挡层空穴反阻挡层空穴反阻挡层空穴反阻挡层:WsWmEFsEFmEvEcE0Contact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band Diagram接触后：接触后：EFEcEvxDContact
14、between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band Diagram7.1.3表面态对接触势垒的影响表表 面面 态：态：局域在表面附近的电子态。局域在表面附近的电子态。表面能级：表面能级：与表面态相应的能级称为表与表面态相应的能级称为表
15、 面能级。面能级。Contact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramE0EFmWmWsWlEvEFS0EF0表面能级表面能级A、接触前，半导体体内与表面电、接触前，半导体体内与表面电 子态未交换电子子态
16、未交换电子 Contact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramB、接触前，半导体体内与表面电子态交换电子后、接触前，半导体体内与表面电子态交换电子后 能带弯曲量能带弯曲量 qVD=EF0-EFs0 与金
17、属的性能无关与金属的性能无关 半导体的功函数则变为：半导体的功函数则变为：EFmWlqVDEnqVDEFsWmWlE0EvEFEcContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramC、金属与半导体接触后
18、、金属与半导体接触后qVD Ec（0）EcEvContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band Diagram 实际中，实际中，实际中，实际中，E EFsFs0 0常位于常位于常位于常位于E Ev v以上以上以上以上
19、1/3E1/3Eg g处，所以处，所以处，所以处，所以Contact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band Diagram当半导体的表面态密度很高时，由于它可以屏蔽金属接触的影响，使半导体内的势垒高度和金属的功函数几乎无
20、关，而基本上由半导体的表面性质决定，接触电势差全部落在两个表面之间。*阻挡层的整流特性和整流理论阻挡层的整流特性和整流理论*欧姆接触欧姆接触7.2 金属半导体接触整流理论金属半导体接触整流理论Rectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor Contact 阻挡层的整流特性阻挡层的整流特性 外加电压对阻挡层的作用外加电压对阻挡层的作用外加电压对阻挡层的作用外加电压对阻挡层的作用Rectification Theory of Metal-Semiconduc
21、tor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor Contact整流理论整流理论（1）扩散理论）扩散理论 xdln时时 （2）热电子发射理论）热电子发射理论 xdln时，电子通过势垒区将发生时，电子通过势垒区将发生多次碰撞。多次碰撞。势垒高度势垒高度qVDk0T时，时，势垒区势垒区内内的载流子浓度的载流子浓度0 耗尽区耗尽区Recti
22、fication Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor Contac
23、tRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactVDRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconducto
24、r Contact（加上外加电压在金属上）加上外加电压在金属上）加上外加电压在金属上）加上外加电压在金属上）这种势垒宽度随外加电压的变化而变化这种势垒宽度随外加电压的变化而变化的势垒就是的势垒就是Schottky势垒势垒。Rectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semico
25、nductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor Contact积分积分 Rectification Theory of Metal-Semiconductor ContactRectification Theory of M
26、etal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor Contact讨论：Rectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Th
27、eory of Metal-Semiconductor Contact7.2.2 7.2.2 热电子发射理论热电子发射理论 xdk0 0T思路：思路：(a)Js m(b)Jm s(c)J=Js m+Jm sRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor
28、Contact(a)Js m时：Rectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal
29、-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor Contact Rectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory o
30、f Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Th
31、eory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectificat
32、ion Theory of Metal-Semiconductor Contact（b）Jm sRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor Contact（c）总电流密度）总电流密度JRectification Theory of Metal-Sem
33、iconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor Contact扩散理论扩散理论与与热电子理论热电子理论的差异的差异xdln时：xdln时：Rectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconduc
34、tor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor Contact7.2.3 7.2.3 镜像力和隧道效应的影响镜像力和隧道效应的影响反向特性不饱和反向特性不饱和Rectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semicon
35、ductor ContactRectification Theory of Metal-Semiconductor Contact势垒受到镜象力的影响：势垒受到镜象力的影响：Rectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor Contact（1）镜象力的影响
36、）镜象力的影响Rectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor Contact感应电荷对电子产生库仑吸引力感应电荷对电子产生库仑吸引力 镜象力镜象力Rectification Theory of Metal-Semiconductor ContactRec
37、tification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor Contact对于金属对于金属-半导体接触势垒中的电半导体接触势垒中的电子，附加势能为子，附加势能为 Rectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRect
38、ification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor Contact 取势能零点在取势能零点在EFm处，考虑处，考虑附加势能后，附加势能后，电子的有效势能电子的有效势能为：为：Rectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor Co
39、ntactRectification Theory of Metal-Semiconductor Contact当电子所受到的电场力当电子所受到的电场力=镜像力镜像力时，有时，有 Vmax=V（xm）Rectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor Con
40、tactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconduct
41、or ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semic
42、onductor Contactn镜向力导致反向特性不饱和Rectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor Contact（2）隧道效应的影响）隧道效应的影响:Rectification Theory of Metal-Semiconductor Cont
43、actRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor Contact决定隧道穿透几率的两个因素：决定隧道穿透几率的两个因素：（1 1）势垒高度）势垒高度 （2 2）隧道厚度）隧道厚度v隧道穿透的临界厚度为隧道穿透的临界厚度为xc，当半导体一边的当半导体一边的势垒厚度势垒厚度 xxc 时，势垒对电子完全时，势垒对电子完全透明透明 隧道穿透隧道穿透v1938
44、年，年，W.Schottky提出了基于整流二极提出了基于整流二极管的理论，称为肖特基二极管理论。这一理管的理论，称为肖特基二极管理论。这一理论以金属和半导体功函数差为基础。论以金属和半导体功函数差为基础。v肖特基势垒二极管是多子器件肖特基势垒二极管是多子器件,有优良的高频有优良的高频特性特性.一般情况下一般情况下,不必考虑少子的注入和复不必考虑少子的注入和复合合.v肖特基势垒二极管有较低的正向导通电压肖特基势垒二极管有较低的正向导通电压.7.3少数载流子的注入和欧姆接触7.3.1少数载流子的注入vn型阻挡层，体内电子浓度为n0，接触面处的电子浓度是v电子的阻挡层就是空穴积累层。在势垒区，空穴的
45、浓度在表面处最大。体内空穴浓度为p0，则表面浓度为v加正压时，势垒降低，形成自外向内的空穴流，形成的电流与电子电流方向一致。v空穴电流大小，取决于阻挡层的空穴浓度。v平衡时，如果接触面处有v此时若有外加电压，p(0)将超过n0，则空穴电流的贡献就很重要了。v加正向电压时，少数载流子电流与总电流值比称为少数载流子的注入比，用表示。v加正电压时，势垒两边界处的电子浓度将保持平衡值，而空穴在阻挡层内界形成积累，然后再依靠扩散运动继续进入半导体内部。v因为平衡值p0很小，所以相对的增加就很显著。v对n型阻挡层而言7.3.2欧姆接触v定义不产生明显的附加阻抗，而且不会使半导体内部的平衡载流子浓度发生显著
46、的变化。v实现 反阻挡层没有整流作用，但由于常见半导体材料一般都有很高的表面态密度，因此很难用选择金属材料的办法来获得欧姆接触。隧道效应：重掺杂的半导体与金属接触时，则势垒宽度变得很薄，电子通过隧道效应贯穿势垒产生大隧道电流，甚至超过热电子发射电流而成为电流的主要成分，即可形成接近理想的欧姆接触。v接触电路：零偏压下的微分电阻v把导带底Ec选作电势能的零点，可得v电子的势垒为v令y=d0-x，则v根据量子力学中的结论，x=d0处导带底电子通过隧道效应贯穿势垒的隧道概率为v有外加电压时，势垒宽度为d，表面势为(Vs)0+V，则隧道概率v隧道电流与隧道概率成正比v进而可得到SEMICONDUCTOR PHYSICS