ee2_fall07_HW5 - 17 cm-3 boron atoms and 2 x 10 16 cm-3...

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EE2 (Fall 2007) Home-work: Problem Set 5 Due date: 11-05-2007 {Unless otherwise stated take the material as silicon and n i as 10 10 cm -3 at 300K) 1. Assume the effective mass for electrons and holes are 1.1 m 0 and 0.56 m 0 calculate the difference between E i and (E c +E v )/ 300 K. 2. Explain why electrons are at the bottom of the conduction band and the hole at the top of the valence band. 3. Assuming that the mobility of electrons and holes are 1200 and 450 cm 2 per volt-sec calculate the electrical conductivity of silicon at 300 K in a) intrinsic silicon b) a piece of silicon containing 10 15 cm -3 phophorous atoms and c) a piece of silicon containing 10
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Unformatted text preview: 17 cm-3 boron atoms and 2 x 10 16 cm-3 arsenic atoms. 4. If in a piece of silicon at 300 K the hole density is 6 x 10 15 cm-3 what is the type and density of impurities? 5. Find the location of E F relative to E i where E i is taken as the middle of the band gap for the material in problem 4. 6. Problem 6 on page 99 of the courses reader. 7. Problem 7 on page 99 in the course reader. 8. A silicon bar of length 3 mm and 200 μ m 2 cross-sectional area contains 5 x 10 18 cm-3 boron atoms. What is its resistance? (Take the hole mobility to be 125 cm 2 /V-sec.)...
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