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# sol3 - ECE 440 HW3 Solutions Summer 2009 Tue 1 Calculate...

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ECE 440 HW3 Solutions Summer 2009 Tue, Jun 30, 2009 1 1. Calculate both the electron and hole concentrations for a germanium sample doped with 2x10 16 arsenic atoms/cm 3 (a) at room temperature (b) at 450 K. Doping germanium with arsenic will make the sample n-type. Thus, N D = 2x10 16 cm -3 . To find the concentrations, one should solve equations (3-27) and (3-24) in S&B simultaneously. (1) 2 i o o n p n = (2) D o A o glyph817 p glyph817 n + = + (a) At room temperature Combining (1) and (2) along with n i from Figure (3-17) is enough to find the electron concentration (3) 3 16 16 2 13 10 2 10 2 ) 10 5 . 2 ( = + = cm x x n x n o o The hole concentration follows from equation (1): (4) 3 10 2 13 10 125 . 3 ) 10 5 . 2 ( = = cm x n x p o o (b) At 450 K Combining (1) and (2) along with n i from Figure (3-17) is enough to find the electron concentration (4) 3 16 16 2 16 10 41 . 2 10 1 ) 10 1 ( = + = cm x x n x n o o The hole concentration follows from equation (1): (5) 3 15 2 13 10 14 . 4 ) 10 5 . 2 ( = = cm x n x p o o 2. A germanium sample is doped with 1x10 14 /cm 3 acceptors and 4x10 13 /cm 3 donors. (a) What are the electron and hole concentrations respectively at room temperature under equilibrium conditions? (b) What are the electron and hole concentrations respectively

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sol3 - ECE 440 HW3 Solutions Summer 2009 Tue 1 Calculate...

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