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# sol5 - ECE 440 HW5 Solutions Summer 2009 Tue 1 Consider a...

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ECE 440 HW5 Solutions Summer 2009 Tue, Jul 07, 2009 1 1. Consider a silicon sample at 300 K. Assume that the hole concentration varies linearly with distance. At x=0, the hole concentration is p(0). At x=10 µm, the hole concentration is p(10 µm)= 5x10 14 /cm 3 . If the hole diffusion coefficient, assumed constant, is D p =14 cm 2 /sec, determine the hole concentration at x=0 for the following two diffusion current densities: (a) the diffusion current density is found to be J p diff = + 0.19 A/cm 2 and (b) J p diff = - 0.19 A/cm 2 . The expression for the diffusion current is in 4-22b. We can replace the derivative with the slopes of the hole concentration. Thus, 2. The donor 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 online), and the sample is at thermal equilibrium at 300 K. X (µm) 0 10 17 /cm 3 N d 10 16 /cm 3 1 2 3 4 5 6 7 8 A B C

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ECE 440 HW5 Solutions Summer 2009 Tue, Jul 07, 2009 2 (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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sol5 - ECE 440 HW5 Solutions Summer 2009 Tue 1 Consider a...

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