hw6_solutions - ECE 440 Homework VI Due Wednesday Fall 2008...

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ECE 440 Homework VI Fall 2008 Due: Wednesday, October 08, 2008 1. Consider a silicon sample at 300 K. Assume that the electron concentration varies linearly with distance. At x=0, the electron concentration is n(0). At x=10 μm, the electron concentration is n(10μm)= 5x10 14 /cm 3 . If the electron diffusion coefficient, assumed constant, is D n =30 cm 2 /sec, determine the electron concentration at x=0 for the following two diffusion current densities: (a) the diffusion current density is found to be J n diff = + 0.9 A/ cm 2 and (b) J n diff = - 0.9 A/cm 2 . 2. The acceptor profile of a silicon sample is shown below. Assume that the majority carrier mobility can be obtained from Fig. 3-23 (or the enlarged graph posted in the 440 website), and the sample is at thermal equilibrium at 300 K. (a) Determine the diffusion coefficients for majority carriers at points A, B and C, respectively. To find the diffusion coefficients, we have to first find the doping concentrations at those
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hw6_solutions - ECE 440 Homework VI Due Wednesday Fall 2008...

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