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20075EE2_1_problem_set4 - 2 2s 2 3p 2 for Carbon 5...

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EE2 (Fall 2007) Home-work: Problem Set 4 Due date: 10-29-2007 1. Assume the effective mass of electrons and holes in silicon is m c = 0.29 m 0 and m v = 0.57 m 0 , calculate the carrier densities at a temperature of 150 0 C. Take the value of electron in vacuum, m 0 , to be 9.1 x 10 -31 kg, the value of Boltzmann constant k to be 1.38 x 10 -23 J/0 0 K and the energy band gap E g to be 1.12 eV.at this temperature. 2. Assume the material is germanium, the band gap is 0.72 eV, the temperature is 300 0 K and the effective mass of the carriers is the same as the mass of electron in vacuum. Calculate the density of intrinsic carriers at this temperature. 3. Taking the effective mass of the carriers to be the same as what is given in problem 1, determine the position of the Fermi level in intrinsic silicons at room temperature (300 0 K). 4. The atomic number of chlorine is 17. Write down the electron configuration for this atom in the format such as 1s
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Unformatted text preview: 2 2s 2 3p 2 for Carbon. 5. Calculate the number of states Z c (E) with energy equal to or less than .05 eV above E c in the conduction band. Take the effective mass of the electron to be 0.29m and not varying in this range of energy values. 6. Derive the expression for the location of E i in the band gap (given on page 20 in the handouts of class 8, 7. A piece of silicon contains 4 x 10 16 cm-3 phosphorous atoms as impurities and assume they are all ionized at room temperature. Taking n i as 10 x 10 10 cm-3 , what are the type and density of majority and minority carriers? 8. A n-type silicon with 10 15 cm-3 donor atoms is exposed to a stream of boron atoms at high temperature so that the borom atoms will diffuse throughout the sample of silicon and make the density of boron atoms to be 10 16 cm-3 . What is the net impurity and type of silicon?...
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