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Unformatted text preview: ECE 440 Homework VI Spring 2008 1. (a) Construct a semilogarithmic plot such as Fig. 47 for Si doped with 4x10 16 /cm 3 donors and having 4x10 14 EHP/cm 3 created uniformly at t = 0. Assume that τ n = τ p = 2 μ s. How much time is needed before the minority carrier concentration equals the intrinsic carrier concentration? The general solution of the equation governing recombination, equation (47), is (1). (1) C Ae t p t + = τ ) ( The boundary conditions of this differential equation are (2) and (3). (2) p t p ∆ = = ) ( (3) ) ( p t p = +∞ → Combining the general solutions and boundary conditions we find that the closed form equation for this system are (4) and (5). (4) ) ( p pe t p t + ∆ = τ (5) ) ( n ne t n t + ∆ = τ Substituting the values from the problem we find numerical functions (6) and (7). (6) τ t e t p ⋅ × = 14 10 4 ) ( (7) 16 14 10 4 10 4 ) ( x e t n t + ⋅ × = τ To plot these functions, use the “semilogy” function in Matlab or a similar program. To plot these functions, use the “semilogy” function in Matlab or a similar program....
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 Spring '09
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