hw10_solutions - ECE 440 Homework X Due: Monday, November...

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ECE 440 Homework X Fall 2008 Due: Monday, November 10, 2008 1. A Schottky barrier is formed between a metal having a work function of 4.7 eV and n-type Si (electron affinity = 4 eV). The donor doping in the Si is 2x10 17 /cm 3 . (a) Draw the equilibrium band diagram showing a numerical value for qV o . The semiconductor work function is the energy difference between the vacuum level and the Fermi level of the semiconductor. eV x x n N kT E q E E E q q i d g i f g S 12 . 4 10 5 . 1 10 2 ln 0259 . 0 2 1 . 1 0 . 4 ln 2 ) ( 2 10 17 = - + = - + = - - + = Φ χ Since this is a junction between a metal and an n-type semiconductor, the barrier height is determined by the energy difference between the conduction band edge and the metal work function. If this were a p-type semiconductor, the barrier height would have been the energy difference between the metal work function and the valence band edge. The contact potential is the difference between the metal work function and the semiconductor work function. This makes a lot of sense intuitively, because it tells
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you that the effective barrier that an electron sees when traveling from the semiconductor to the metal is the difference in their work functions.
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This note was uploaded on 10/14/2009 for the course ECE 440 taught by Professor Lie during the Spring '09 term at University of Illinois at Urbana–Champaign.

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hw10_solutions - ECE 440 Homework X Due: Monday, November...

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