20101ee2_1_HW4 solution

# 20101ee2_1_HW4 solution - EE2 HW4 Solutions Winter 2010...

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EE2 HW4 Solutions Winter 2010 Problem 1 The thermal equilibrium values of the minority carrier densities in the neutral n and p regions can be found using the law of mass action: 3 4 2 10 = = cm N n p D i no 3 3 2 10 * 2 = = cm N n n A i po We know from the Boltzmann relations that the excess carrier distributions at the edge of the space charge region in the neutral regions of the junction is: Δ p(x = x n ) = p no [exp(qV F /kT) - 1] Δ n(x = -x p ) = n po [exp(qV F /kT) - 1] Therefore, Δ p(x = x n ) = 10 4 [exp(0.4/0.0259) – 1] = 5.096 x 10 10 cm -3 . and Δ n(x = -x p ) = 1.019 x 10 10 cm -3 . p - n + + + - - - x p x n + N A =5x10 16 cm -3 N D =10 16 cm -3 ) Δ p(x=x n ) Δ n(x=-x p

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Problem 2 ssume that the diode is a wide base diode. a) I) The current due to electron injection is given by We know that the applied voltage is V F = 0.4V and A = 4x10 -4 cm 2 . We need to find the currents through the junction at the specified bias. We are also asked to a nA A I kT qV L n qAD I n n
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20101ee2_1_HW4 solution - EE2 HW4 Solutions Winter 2010...

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