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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 7.1 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 Diagram7.1.1 7.1.1 金属和半导体的功函数EcEvWmWsEFmEFsE0EnContact b
2、etween 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 7.1.2 接触电势差接触电势差Contact between Metal and Semiconductor and Band DiagramContact
3、 between Metal and Semiconductor and Band DiagramContact between 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间间间间隙中隙中电势电势电势电势 差，差，导带
4、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度：度：qVqVDD=-=-qVqVs s=W=Wmm-W-Ws s（1 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：qVDEc EFEvContact between Metal and Semiconductor 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 Semico
5、nductor and Band DiagramContact between Metal and Semiconductor and Band Diagram（1 1）金属）金属-n-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 Diagram（a a） WWmmWWs s电子阻挡层电子阻挡层: :Contact between Metal and Semiconductor and Band Diagr
6、amContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band Diagram金属一边的势垒 半导体一边的势垒 Contact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band Diagram（
7、b b） WWmmWWm m 空穴阻挡层空穴阻挡层: : EFmEFsWsWmEvEcE0Contact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band Diagram接触后：接触后：qVD=Ws-Wm xDEF EvEcContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band Diagram（2 2
8、）WWmmWWs s 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 Diagram接触后：接触后：EFEcEvxDContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band Diagram7.1.37.1.3表面态对接触势垒
9、的影响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 面能级。面能级。Contact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramE0EFmWmWsWlEvEFS0EF0表面能级表面能级AA、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未交换电子Contact between Metal and
10、 Semiconductor and Band DiagramContact between Metal and Semiconductor and Band DiagramBB、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 qVD=EF0-EFs0 与金属的性能无关 半导体的功函数则变为： EFmWlqVDEnqVDEFsWmWlE0EvEFEcContact between Metal and Semiconductor and Band DiagramContact between Metal and Semiconductor and
11、Band DiagramC C、金属与半导体接触后、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 Diagram实际中，实际中，E EFsFs0 0常位于常位于E Ev v以上以上1/3E1/3Eg g处，所以处，所以Contact between Metal and Semiconductor and Band DiagramContact between Metal and Semi
12、conductor 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 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
13、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Rectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor Contact整流理论整流理论（1 1）扩散理论）扩散理论 x xd dl ln n时时 （2 2）热电子发射理论）热电子发射理论 x xd dl ln n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qVqVDDkk0 0T T时，时，势垒区势垒区内内 的载流子浓度的载流子浓度0 0 耗尽区耗尽区Rectific
14、ation Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactVDRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor Contact
15、（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 的势垒就是SchottkySchottky势垒势垒。Rectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor Contact积分 Rectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor Contact讨论：讨论：Rectification Theory of Metal-Semiconductor ContactRectification Theory of Metal-Semiconductor Contact7.2.2 7.2.2 热电子发射理论热电子发射理论x xd dkk0 0T T思路：思路：(a) Js m (b) Jm
