半导体物理学半导体 (36).pdf
![资源得分’ title=](/images/score_1.gif)
![资源得分’ title=](/images/score_1.gif)
![资源得分’ title=](/images/score_1.gif)
![资源得分’ title=](/images/score_1.gif)
![资源得分’ title=](/images/score_05.gif)
《半导体物理学半导体 (36).pdf》由会员分享,可在线阅读,更多相关《半导体物理学半导体 (36).pdf(30页珍藏版)》请在得力文库 - 分享文档赚钱的网站上搜索。
1、Metal-Semiconductor and Semiconductor Heterojunctions(金半接触和半导体异质结)Schottky Barrier Diode01Metal-Semiconductor Ohmic Contacts02Heterojunctions03Schottky Barrier DiodeQualitative characteristics 01Ideal junction properties02Non-ideal effect on the barrier height03Current-voltage curve04Comparison betw
2、een schottky and pn diodes 05Schottky diode structures(a)Point contact (b)Face contactMetal-semiconductor diode was developed from 1920s,which is formed of point contact between metal and bare semiconductor.These metal-semiconductor diodes are hard to fabricate,and reliability is also bad,so it is r
3、eplaced by pn junction in 1950s.With the development of semiconductor and vacuum technique,metal-semiconductor contact can be achieved.Schottky barrier diodeSchottky barrier diodeEnergy bands of metal and n-type semiconductor are shown.Semiconductor work function s:the difference between Ef and vacu
4、um energyMetal work function m:The lowest energy needed by electron emitting from metal to vacuum.Electron affinity :The lowest energy needed by electron emitting from Ec to vacuum energy.Qualitative characteristicsEnergy-band diagram of a metal and semi conductor before contactElectronic affinity o
5、f several semiconductorsCu,copper 4.65Work functions of metals and electron affinity of semiconductors m sIdeal thermal equilibrium energy band diagram.The Ef of semiconductor is higher than that of metal.The electrons move from semiconductor to metal,and fixed donor atom with positive charge is lef
6、t at semiconductor,forming the space charge region.Figure(a)Energy-band diagram of a metal and semiconductor before contact;(b)ideal energy-band diagram of a metaln-semiconductor junction for ms.Electronic affinity of several semiconductorsThe ideal barrier height B0Vbi is built-in voltageSchottky b
7、arrier m s=m-sIf a negative bias is applied between metal and semiconductor,barrier will increase,while B0 keep unchanged.Reverse-biased voltage m sForward-biased voltage m sIf a positive bias is applied between metal and semiconductor,barrier will decrease,while B0 keep unchanged.It is different to
8、 pn junction,current is dominated by majority carrier electrons.Under a forward bias,barrier decrease,and electrons move from semiconductor to metal more easily.Forward current is from metal to semiconductor,and current is the exponential function of Va.msSchottky diode property Electrostatic proper
9、ties The electric field in the space charge region is determined from Poissons equation.Ideal junction propertiesThe electric field is zero at the space charge edge in the semiconductor,so the constant of integration is If the semiconductor doping is uniform.The electric field can be written as wher
10、e VR is the magnitude of the applied reverse-biased voltage.Electric field and width of space charge region?=?=?2?(?+?1 2?=?(?)The space charge region width is similar to the p+n junction.Since the E-field is zero inside the metal,a negative surface charge must exist in the metal at the metal-semico
11、nductor junction.Ideal junction properties A junction capacitance can also be determined in the same way as we do for the p+n junction.where C is the capacitance per unit area.If we square the reciprocal Junction capacitance of Schottky barrier diode:?=?=?2(?+?1 2?1?=2(?+?We can obtain the built-in
12、potential barrier Vbi.The slope of the curve can calculate the semiconductor doping Nd.Combing with n,the Schottky barrier B0 can be calculated.Ideal junction propertiesThe built-in potential barrier and doping concentration of the GaAs Schottky diode are larger than that of the silicon diode.?1?=2(
13、?+?Ideal junction propertiesn Several effects alter the actual Schottky barrier height from the theoretical value.n The Schottky effect,or image-force-induced lowering of the potential barrier.n An electron in a dielectric material at a distance x from the metal will create an electric field.The ele
14、ctric field can be determined by adding an image charge,e,inside the metal located at the same distance.Non-ideal effect on the barrier heightSchottky effect,the mirror image force reduction effect of the barrier.eB0eSchottky barrier reduction Xm corresponding to the maximum barrier?=?16?=?4?Non-ide
15、al effect on the barrier heightWithout mirror image forceWith mirror image forceMirror image potentialMeasured barrier heights in GaAs and silicon Schottky diodes as a function of metal work functions.However,the barrier height and metal work function curves do not fit the monotonic relation.The bar
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- 半导体物理学半导体 36 半导体 物理学 36
![提示](https://www.deliwenku.com/images/bang_tan.gif)
限制150内