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EE 2 HW 2 09Spring-PS2 - QN

# EE 2 HW 2 09Spring-PS2 - QN - part b Question#4(5 points...

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EE2 Problem Set#2 Due 4/22/09 in class Question #1: (5 points) Describe the difference between unipolar and bipolar conduction. Question #2: (5 points) The density of states in the conduction band increases with the square root of energy. Why then, can we state that most of the electrons are near the band edge, E c ? Question #3: (15 points): (a) Show that the Fermi function is symmetric about E F , i.e., f E F + Δ E ( ) = 1 f E F − Δ E ( ) (b) Show that when E E F ( ) >> kT , f E ( ) e E E F kT . (c) Calculate f(E) for (E–E F ) equal to 2kT, 3kT, and 4kT by using the Fermi function. Compare the results with those obtained using the Maxwell-Boltzmann approximation in
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Unformatted text preview: part b. Question #4 (5 points): The position of an electron is determined to within 1 angstrom. What is the minimum uncertainty in its momentum? Question #5 (10 points): (a) If your Fermi level is at E c , what is the probability of finding an electron at E = E c + kT? (b) If your Fermi level is at E v , what is the probability of finding a hole at E = E v – kT? Question #6 (5 points): You dope intrinsic silicon with Arsenic at 10 17 atoms/cm 3 . (a) What is the concentration of electron charge carriers at room temperature? (b) What is the concentration of holes?...
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