20082ee2_1_homework%204_08

20082ee2_1_homework%204_08 - VI. Find out the thermal...

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. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . EE2 Physics for Electrical Engineers Homework #4 I. Explain the density of states and effective density of states. II. Find out the number of quantum states per cubic centimeter at the conduction band edge of GaAs with energy between zero and 0.026 meV. III. Use the density of states concept and Boltzmann statistics to derive the Maxwell- Boltzmann distribution function that you learned in kinetic theory of gases. IV. Find out the fraction of water molecules at room temperature with speed between sec / 10 2 4 cm × and sec / 10 4 4 cm × . V. The relaxation time of electrons in GaAs is close to picosecond. Estimate the electron mobility in GaAs. Compare the drift velocity of the electron in an electric field of 1 kV/cm and compare it with the final velocity of the ballistic motion from rest. Explain the result of your comparison.
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Unformatted text preview: VI. Find out the thermal velocity of electrons in GaAs at room temperature i. e. the velocity of electrons with an energy of kT 2 3 . Compare it with the final ballistic velocity in Problem V and explain the significance of the comparison. VII. A silicon sample is doped with 3 16 10 cm borons, estimate the conductivity of this sample at room temperature if we can neglect impurity scattering. (It is still a good approximation in this case) VIII. Estimate the mean free time and mean free path of the holes in Problem VII. --END-- Electrical Engineering Department The Henry Samueli School of Engineering and Applied Science University of California, Los Angeles Dee-Son Pan pan@ee.ucla.edu Phone (310)-825-1123 Spring 2008...
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