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2_1_midterm_sample

# 2_1_midterm_sample - angstrom What is the Fermi level at 0...

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Physics for Electrical Engineers Prof. B. Jalali EE 2 Midterm Exam 1. An electron is described by a plane-wave function ) 7 10 ( t x j Ae . Calculate the expectation value of the x-component of momentum, the y-component of the momentum and the energy of the electron. (Give values in MKS units.) 2. An electron has momentum p=1x10 -24 kg x m/s. (a) Find the wavevector k (spatial frequency). (b) Find the De Broglie wavelength. (c) Find the energy of the electron (use the electron rest mass). (d) Find the group velocity of the electron. (e) If the uncertainty in the value of momentum is 1 part per million, what is the uncertainty in electron’s position? (f) Find the frequency f , assuming that the phase velocity v p is equal to half the group velocity v g that you found in part (d): v p = v g /2 3. We put 11 electrons in an infinite 1-D potential well of size 100
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Unformatted text preview: angstrom. What is the Fermi level at 0 K? What is the probability of exciting a carrier to the first excited state at T=300 K? Use the free electron mass in this problem. 4. A Si sample doped with 10 17 As atoms/cm 3 , (a) What is the equilibrium hole concentration p o at 300 K? (b) Where is E F relative to E i ? (c) Is the semiconductor degenerate or non-degenerate? Why? (d) An electric field E = 1 V/cm is applied to the semiconductor. Draw the band diagram (Ec, Ev, and Ei) and indicate the directions of electron and hole flow. In what direction will the total electric current flow? (e) If the average time between collisions is 1 ps, what will be the electron and hole mobilities? (f) Calculate the total drift current density. Assume the same collision time for holes....
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