Exam 3 Solutions

Ece606 4 spring 2013 exam 2 ece 606 spring

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Unformatted text preview: on (MDE) and the boundary conditions for this problem. Make reasonable assumptions. ∂ Δn ∂ 2 Δn Δn From the formula sheet: = Dp − + GL ∂t dx 2 τ n ∂ 2 Δn Δn Simplify for steady state, no generation: 0 = D p − + 0 dx 2 τ n Now check the diffusion length: Ln = Dn! n = 0.026 " 5500 " 10#8 = 12 " 10#4 >> L Since the diffusion length is much greater than the length of the structure, we can neglect recombination and find: d "n d 2 !n ! Dn = SB "n ( L ) = 0 !n ( 0 ) = 1014 2 dx L dx 3b) Sketch the expected steady ­state solution to the MDE for three cases: I) S B = 0 cm/sec, II) S B ! " cm/sec, and III) S B = 105 cm/sec (a moderate value). ECE ­606 4...
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