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Unformatted text preview: rriers uniformly throughout the sample at a rate of g’ = 8 x 1020 cm 3s 1. Assume the minority carrier lifetime is 5 x 10 7 s, and assume mobility values of µn = 900 cm2/Vs and µp = 380 cm2/Vs. (a) Determine the conductivity of the silicon as a function of time for t > 0. (b) What is the value of the conductivity at (i) t = 0, and (ii) t →∞? (b)(i) At t = 0, we have only the background dark conductivity, which is σ (0 ) = ep0 µ p = 1.6 × 10 −19 ⋅ 1016 ⋅ 380 = 0.608 mho − cm (ii) At t → ∞, we add the photoconductivity Δσ = eΔn( µn + µ p )
= e( g′τ n )( µn + µ p )
= 1.6 × 10 −19 ⋅ 8 × 10 20 ⋅ 5 × 10 −7 (900 + 380 ) = 82 mmho − cm and σ (∞ ) = g(0 ) + Δσ = 0.69 mho − cm (a) The time behavior is σ (t ) = σ (o) + Δσ (1 − e− t /τ n ) (...
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This document was uploaded on 02/19/2014.
 Fall '14

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