# HW2 - EE2 Problem Set#2 Solutions Question #1: (5 points)...

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EE2 Problem Set#2 Solutions Question #1: (5 points) Suppose the energy of an electron is given by E ( k ) = 2.74 10 -37 k 2 Joules where k is given in units of meter -1 . Find the effective mass, and give the ratio of the effective mass to the ordinary mass of the electron. E k   2.74 10 37 k 2 Effective mass, m * h 2 d 2 E dk 2 dE dk 2 2.74 10 37 k 5.48 10 37 k d 2 E dk 2 5.48 10 37 m * h 2 d 2 E dk 2 6.625 10 34 2 1 5.48 10 37 2.025 10 32 kg Ratio of effective mass to ordinary mass of electron = m * m 0 2.025 10 32 9.1 10 31 0.022 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 ? The number of carriers is equal to the integral (over energy) of the density of states multiplied by the probability that the state is filled (Fermi-Dirac or Maxwell-Boltzmann statistics).

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## This note was uploaded on 02/28/2011 for the course EE 2 taught by Professor Vis during the Winter '07 term at UCLA.

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HW2 - EE2 Problem Set#2 Solutions Question #1: (5 points)...

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