HW SOLN 4

# HW SOLN 4 - ECE331 Homework#4 Solution 1 Explain the...

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1 ECE331 Homework #4 Solution 1. Explain the concept of electron effective mass. At what scenario the effective mass is the actual electron mass? Use equations if necessary. ± Effective mass is the term used to describe the total effect of forces outside and inside of a crystal lattice. In reference to the band diagram, effective mass is inversely proportional to the band curvature. That is, for high band curvature the effective mass is low, while for low curvature the effective mass is high. Also, at the band minima the effective mass is positive, and at the band maxima (the top of the valence band for example) the effective mass is negative. Negative effective electron mass is the positive effective mass of a hole. ± Effective mass will equal the electron mass only if there are no interior crystal forces, thus only in free space the effective mass is equal to the free electron mass. One equation for effective mass is: k E m = 2 2 * } 2. Explain the concept of direct and indirect semiconductors. Use E-K diagram

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## This note was uploaded on 05/05/2010 for the course ECE 331 taught by Professor Rajan during the Spring '09 term at Ohio State.

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HW SOLN 4 - ECE331 Homework#4 Solution 1 Explain the...

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