hw8 - Assume that the depletion approximation holds. (a)...

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ECE 440 Homework VIII Spring 2006 Due: Friday, March 03, 2006 1. An abrupt Si p-n junction is formed by alloying a uniformly doped n-type silicon bar of which N d = 4x10 16 /cm 3 . During the alloying process, a uniform counter doping of acceptors of N a = 1.5x10 17 /cm 3 is introduced in the region for x<0. For x>0, the doping remains to be N d = 4x10 16 /cm 3 . So, x<0 is the p-side and x>0 is the n-side. (a) Calculate the Fermi level positions at 300 K in the p and n regions. (b) Draw an equilibrium band diagram for the junction and determine the contact potential V o from the diagram. (c) Compare the results of part (b) with V o as calculated from Eq. (5-8). (d) Using Eq. (5-8), calculate and plot V o versus temperature ranging from 250 K to 500 K. 2. Refer to problem 1, the silicon bar has a circular cross section with a diameter of 20 μm.
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Unformatted text preview: Assume that the depletion approximation holds. (a) Calculate W, X no and X po at 300 K. (b) Determine the total positive ion charge in the depletion region. (c) Sketch to scale the charge density (x), electrical field E (x), and electrostatic potential V(x) in the depletion region. Assume that the electrostatic potential is zero at x= 0. (d) Draw the energy band diagram for the device. 3. Refer to problem 1 again. In reality, the alloying process will introduce a much higher concentration of acceptor. Assume that the uniform counter doping is N a = 2x10 19 /cm 3 instead. Determine and plot the contact potential V o and depletion widths W, X no and X po versus temperature ranging from 250 K to 500 K....
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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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