Homework 3-solutions

# Homework 3-solutions - Homework #3, Due Thursday 10/1/09 I....

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Homework #3, Due Thursday 10/1/09 I. (20 points) Calculated the magnitude of the velocity of an electron in GaAs with energy of 3/2 k B T above the conduction band edge (the thermal average energy) with T = 300K, assuming the validity of the effective mass approximation. Repeat for Si, treating the system as isotropic (not directionally dependent) using the conductivity, effective mass. (This actually works.) In each case, put your answers in units of m/s = nm/ns (relevant for current device scales and clock frequencies) and km/hour (relevant to everyday experience). Appendix III may be helpful. Note that the conductivity effective masses are provided in Example 3-6 of the text, or could be calculated for Si as done in the example. (Also, just FYI for now, note that the average velocity of charge carriers through conventional transistors now approaches this velocity.) T k m E B 2 3 2 1 2 v or cond B m T k 3 v For GaAs km/hr 10 6 . 1 m/ps) 45 . 0 ( m/s 10 5 . 4 ) kg 10 109 . 9 ( 067 . 0 ) J/eV 10 602 . 1 )( eV 0259 . 0 ( 3 3 6 5 31 19 cond B m T k v and for Si km/hr 10 3 . 8 m/ps) 23 . 0 ( m/s 10 3 . 2 ) kg 10 109 . 9 ( 26 . 0 ) J/eV 10 602 . 1 )( eV 0259 . 0 ( 3 3 5 5 31 19 cond B m T k v (where the middle answer is not required).

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II. (20 points) Consider conduction-band minimum energy valleys centered at the X
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## This note was uploaded on 10/26/2009 for the course EE 339 taught by Professor Banjeree during the Fall '08 term at University of Texas.

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Homework 3-solutions - Homework #3, Due Thursday 10/1/09 I....

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