314-SampleProblems-F - electrons from a metal 5 A Hall sw itch uses an extrinsic p-type semiconductor doped w ith 10 acceptors per cm 14 3 p The

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4. The density of states N(E) in the valence band of a metal is given by N(E) = 10 E cm eV , w here E is in eV. 22 1/2 -3 -1 M The w ork function N of the metal is 5.0 eV. F (a) Calculate the Fermi energy E if the electron concentration in the metal is 6 x 10 22 cm , assuming T = 0 K for this calculation. -3 (b) Sketch the occupied density of states function f(E)N(E) as a function of E at room temp. Indicate on the diagram the Fermi level and the vacuum level. [f(E) is the Fermi function]. (c) How w ill you calculate (do not calculate) the number of electrons w ith energy above vacuum level at any non-zero temp.? [This is the basis of thermionic emission of
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Unformatted text preview: electrons from a metal]. 5. A Hall sw itch uses an extrinsic, p-type semiconductor doped w ith 10 acceptors per cm . 14 3 p The hole mobility : of the semiconductor is 500 cm /V-sec. The sample is 1 cm x 1 cm 2 square and 1 : m thick. H (a) Is the Hall voltage V (as defined in fig.) positive or negative? H H z (b) For the given sample, calculate the Hall sensitivity S = V /B . (c) What is the advantage of low ering the semiconductor dopant concentration in a Hall device? What happens if the semiconductor is intrinsic? Assume equal hole and electron mobilities....
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This note was uploaded on 10/16/2010 for the course E SC 314 at Pennsylvania State University, University Park.

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