hw50902 - voltmeter with copper leads to contacts on...

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ECE G201 H.W. #5, Due February 24, 2009 1. 4.1, text 2. 4.2, text 3. 4.5, text 4. 5.1, text. 5. 5.2, text. 6. A silicon step junction N A = 4X10 18 /cm 3 (assume non-degenerate), ND = 10 16 /cm 3 , is at 300K. Calculate the following in equilibrium, assuming the depletion approximation. a. V bi b. x n , x p , and W c. n po and p no d. Percentage of the depletion region on the p-side 7. For the diode in the previous problem: a. Determine the junction capacitance for an applied voltage of 0 V. b. Determine the saturation current, assuming τ n = τ p = 10 -6 sec. c. Recompute a. and b. for a change in N A to 4X10 17 . d. Recompute a. and b. for a change in ND to 10 15 , keeping N A at 4X10 18 . e. Which change has a larger effect on the characteristics? 8. An attempt to measure the internal contact potential of a p-n junction is made by connecting a
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Unformatted text preview: voltmeter with copper leads to contacts on opposite sides of the junction. The voltmeter reads zero. Explain the failure of this method. 9. Derive the I-V characteristics of the short-base diode shown, where the boundary condition at the contact on the n-side is given by Sp very large (equivalent to saying that the excess minority carrier concentration is zero). Note that this is not in either limit discussed in the text! You need to do the diffusion problem including both positive and negative exponentials. xn' - xn is on the order of Lp, xp' - xp >> Ln. Lp and Ln are the minority carrier diffusion lengths....
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