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Unformatted text preview: ECE 440 Homework V Fall 2008 Due: Monday, September 29, 2008 1. How long does it take an average electron to drift 0.2 mm in (a) pure Si and (b) Si doped with 6x10 16 /cm 3 donors at an electric field of 100 V/cm? Repeat for 10 5 V/cm. Assume that the electron effective mass m n *=0.26 m o . 2. (a) Construct a semilogarithmic plot such as Fig. 4-7 for GaAs doped with 1x10 17 /cm 3 acceptors and having 3x10 15 EHP/cm 3 created uniformly at t = 0. Assume that τ n = τ p =60 ns. (b) Calculate the recombination coefficient α r for part (a). (c) Assume that this value of α r applies when the GaAs sample is uniformly exposed to a steady-state optical generation rate g op = 10 22 EHP/cm 3-s. Find the steady-state excess carrier concentration ∆ n = ∆ p. The general solution of the equation governing recombination, equation (4-7), is (1). (1) C Ae t p t + =- τ ) ( The boundary conditions of this differential equation are (2) and (3)....
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This note was uploaded on 10/14/2009 for the course ECE 440 taught by Professor Lie during the Spring '09 term at University of Illinois at Urbana–Champaign.
- Spring '09