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Unformatted text preview: (b) Use the concept of electrochemical potentials to explain the difference between a metal-metal junction and a battery. For example, why cant we measure with a voltmeter the potential difference across an Al/Pt junction, whereas we have no trouble measuring the voltage across a battery? 2. Doping Dependence of Carrier Concentrations in GaAs Consider GaAs doped with Te ( E c E d = 0.030 eV). Assume that N c = 4.7 x 10 17 cm-3 , N v = 9.5 x 10 18 cm-3 and a bandgap of 1.42 eV. (a) Determine n i 2 at 300 K. (b) Determine np/n i 2 as a function of N d , the donor density. In particular, at what doping density does np deviate from n i 2 by as much as 10%? What happens when N d gets very large (large enough, for example, to have E F between E c and E d )? + V B - Copper Wires Al SiO 2 100 nm Pt q Al = 4.1ev q Pt = 5.1ev...
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This note was uploaded on 01/04/2012 for the course APH 183b taught by Professor List during the Fall '09 term at Caltech.
- Fall '09