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Unformatted text preview: ECE 440 Homework VII Fall 2008 Due: Monday, October 20, 2008 1. An abrupt Si pn junction has N a = 6x10 16 /cm 3 on the pside and N d = 2x10 17 /cm 3 on the n side. (a) Calculate the Fermi level positions at 300 K in the p and n regions. P region: (1) eV n p q kT E E i f i 394 . 10 5 . 1 10 6 ln 0259 . ln 10 16 = × × ⋅ = = N region: (2) eV n n q kT E E i i f 425 . 10 5 . 1 10 2 ln 0259 . ln 10 17 = × × ⋅ = = (b) Draw an equilibrium band diagram for the junction and determine the contact potential V o from the diagram. First draw the Fermi level straight across (the sample is in equilibrium). Then, draw E c and E v in both the p and n regions based on the calculations in part (a). V can be determined graphically by summing (1) and (2). (3) eV qV 819 . 425 . 394 . = + = (c) Compare the results of part (b) with V o as calculated from Eq. (58). (4) ( 29 V n N N q kT V i A D 819 . 10 5 . 1 10 6 10 2 ln 0259 . ln 2 10 16 17 2 = × × ⋅ × ⋅ = ⋅ = (58) As you can see, the results in part (b) and (c) are identical. As an exercise, try deriving As you can see, the results in part (b) and (c) are identical....
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 Fall '09
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 Trigraph, depletion region, contact potential Vo

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