quiz230B-1_2010_solution

# quiz230B-1_2010_solution - +-p diode dominated by electron...

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ECE 230B Quiz-1 (Winter 2010) Assume silicon, room temperature, complete ionization. Consider an abrupt n + -p junction with p-type doping of N a = 10 17 cm -3 . (a) What is the built-in potential? (b) If both contacts are 0.1 cm away from the junction, estimate the current density at a forward bias of 0.75 V. (c) Estimate the voltage (IR) drop in the p-region due to this current. Solutions: (a) ψ bi = E g /2 q + ( kT / q )ln( N a / n i ) = 0.98 V. (b) Current of an n
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Unformatted text preview: +-p diode dominated by electron diffusion in p-type region. Electron diffusion length L n in p-type is ~ 100 μ m << contact distance W = 0.1 cm, i.e., a wide-base diode and J n = [ μ n kTn i 2 / N a L n ]exp( qV app / kT ) n ~ 1000 cm 2 /V-s, so J n ~ 1.35 A/cm 2 . (c) Resistivity of p-type, N a = 10 17 cm-3 : ρ ~ 0.2 Ω-cm. Field E = J n = 0.27 V/cm IR drop in p-region = W× E = 27 mV....
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## This note was uploaded on 10/09/2010 for the course ECE 230 at UCSD.

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