Sample_Exam_1_Answers

Sample_Exam_1_Answers - a) The intrinsic carrier...

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a) The intrinsic carrier concentration is calculated by integrating the Fermi function / density of states function product. Using this fact, explain why the intrinsic carrier concentration increases with increasing temperature. The Fermi function broadens as temperature increases. Therefore, the integral of f*g also broadens as temperature increases, resulting in more electrons in the conduction band and more holes in the valence band. b) Suppose I take a piece of silicon and measure its Fermi level to be exactly at midgap. Is the semiconductor intrinsic, n-type, or p-type? Justify your answer with equations as appropriate. The semiconductor will be slightly n-type. Since N C is larger than N V , the intrinsic level is actually slightly below midgap : Note: In the review session, it was incorrectly stated that mp >mn. For Silicon, mp = 0.56me, and mn =1.08me. Thus, Ei is slightly LESS than (Ec+Ev)/2, and the semiconductor is n-type. c) Suppose I take a piece of Si and measure its electron concentration to be 10
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This note was uploaded on 10/14/2008 for the course EE 143 taught by Professor Alijavay during the Spring '08 term at Berkeley.

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Sample_Exam_1_Answers - a) The intrinsic carrier...

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