EE 305 HW#4b

EE 305 HW#4b - illumination of a semiconductor are...

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ECE 305 Homework #4 Due Wednesday, February 17 Problem 1: At x = 0, the injector maintains a steady state excess hole concentration of p(0) = 10 10 cm -3 and the extractor at x = 10 -6 cm maintains p(10 -6 cm) = 0. a) Do low level injection condition exist throughout the semiconductor? Why or why not? b) You can ignore recombination in the semiconductor, which means every injected hole at x = 0 makes it to x = 10 -6 cm. How can you deduce that? c) Find an expression for p(x) in the semiconductor. d) Is there a hole current? If so, what is it? Problem 2: (see fig on next page). The equilibrium and steady state conditions before and after
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Unformatted text preview: illumination of a semiconductor are characterized by the energy band diagrams shown below. For this semiconductor at T = 300 K, n 1 = 10 9 cm-3 , p = 500 cm 2 Vs , and n = 5000 cm 2 Vs . a) Determinen o and p o the equilibrium carrier concentrations. b) Determine n and p under steady state conditions. c) What is N A ? d) Do we have low-level injection when the semiconductor is illuminated? Explain. e) What is the resistivity of the semiconductor before and after illumination? 10-6 cm x (cm) n o = 10 17 cm-3 p o = 10-3 cm-3 Lp = 10-4 cm injector extractor...
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EE 305 HW#4b - illumination of a semiconductor are...

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