hw7 - ECE 440 Homework VII Spring 2006 Due: Wednesday,...

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ECE 440 Homework VII Spring 2006 Due: Wednesday, February 22, 2006 1. The donor profile of a silicon sample is shown below. Assume that the majority carrier mobility can be obtained from Fig. 3-23, 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. (b) Find the majority carrier diffusion current densities along the cross sections at points A, B and C, respectively. Indicate not only the magnitude but also the direction. (c) Find an expression for the built-in electric field E (x) at equilibrium over the range from x= 1μm to x=3 μm. (d) Sketch a band diagram such as in Fig. 4-15 over the range from x= 1μm to x=3 μm and indicate the direction of E . 2. A bar of silicon has a donor doping profile of n(x) = N o exp{-Ax 2 } where A is a constant. Derive an expressing for the built-in electric field as a function of x. If A = 5.6 x 10 7 /cm 2 , determine the position at which the electric field is 10
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hw7 - ECE 440 Homework VII Spring 2006 Due: Wednesday,...

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