EE 305 HW#6 - (Yes, you have enough information to get a...

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ECE 305 Homework #6 Due Wednesday, March 24 Problem 1: A pn heterojunction is one in which the p- and n- regions are different semiconductors. You are given a pn-heterojunciion where the p-material is normal Si, i.e. n i = 1x10 10 cm - 3 and the n-region is a mixture of SiGe and has n i = 1x10 11 cm - 3 . Also, the quasi- neutral region thickness on both the p and n sides of the ideal diode have the same value, d, which is << than either L p or L n . Otherwise, N A =N D , Ln=Lp, and Dn=Dp. There is no recombination in the depletion region of the diode. a) Derive the symbolic I-V equation, i.e. I = I o (e qVA/kT -1) and determine the I o term for the boundary condition of this problem. b) Recognizing that I = I p + I n , what is the numerical ratio of I p /I n in the depletion region?
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Unformatted text preview: (Yes, you have enough information to get a numerical answer!) Problem 2: A GaAs step pn-junction diode has N A = 10 17 cm-3 , N D = 10 15 cm-3 , and exhibits a breakdown voltage of 400V at T = 300K. a) What is the breakdown mechanism in this diode? b) Calculate the critical electric field. (Ks = 12.9 for GaAs) c) Approximately what would you change the donor doping to in order to obtain a diode with a breakdown voltage of 600V? Problem 3: A diode has an n=2 (R-G) saturation current of 10-10 A, an n=1 (diffusion) saturation current of 10-14 A , and a series resistance of 1 Ω . Determine the voltage drop across the diode for the currents shown in the table Current Voltage drop 4.75 nA 5.5 mA 0.1 A...
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This note was uploaded on 03/25/2011 for the course ECE 305 taught by Professor Melloch during the Spring '08 term at Purdue University.

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