hw10_solutions - ECE 440 Homework X Spring 2006 Due:...

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Homework X Spring 2006 Due: Wednesday, March 15, 2006 1. A n + -p Si junction with a long p-region has the following properties: N a =2x10 16 /cm 3 ; μ n = 1000 cm 2 /V-s; μ p = 360 cm 2 /V-s; τ n =1 μs. If we apply 0.75 V forward bias to the junction at 300 K, what is the electric field in the p-region far from the junction? Draw a band diagram in the p-region far from the junction assuming that the junction is at x=0 and the p-side is in x>0. Since this is a n + -p junction, we can ignore the contribution of holes to the diffusion current. Similarly to the last two problems, we can find s cm u q kT D n p n / 9 . 25 2 = = cm D L p n p n p n 00509 . = = τ 3 2 250 , 11 = = cm p n n p i p so cm A e n L D q x J J kT qV p p n p n p diff n / 5 . 34 1 ) 0 ( = = = . On the p side, far from the junction, the contribution of diffusion current approaches zero while the drift current due to holes is dominant. Since current must be continuous along the x-direction we know the drift current far from the junction will be equal to the diffusion current near the junction. ) ( ) ( ) ( ) 0 ( x E x p q x J x J p p n drift p p diff n µ = = cm V x p q x J x E p p p diff n / 9 . 29 10 2 360 10 6 . 1 5 . 34 ) ( ) 0 ( ) ( 16 19 = = = = Once we have an equation for E(x) we can construct the band diagram. Notice that region.
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This note was uploaded on 12/01/2011 for the course ECE 340 taught by Professor Leburton during the Spring '11 term at University of Illinois, Urbana Champaign.

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hw10_solutions - ECE 440 Homework X Spring 2006 Due:...

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