Question

Problem 2 (25 points) In a silicon semiconductor, excess carriers are being generated at x -0 as shown below. Assume NA 2x1015 cm3, N 0. The excess carrier concentration at x-0 is 1013 cm3 and the excess carrier concentration at x = Ln is 0 (Ln ls the electron diffusion length). lụs, are D,-25 cm2/s, D,-10 cm2/s. Assume the electric field is zero, ta T = 300K. ķT1e = 0.026V. tp Light NA 2x1015 cm3 a) (15 points) Write the minority carrier diffusion equation and determine n(x). b) (10 points) Determine the electron diffusion current density at x 0.

Answer 1

N_A = 2 Times 10^15 cm^- 3 m, N_D = 0 Delta P = Delta n = 10^3 cm^- 3 at x = 0 Delta P = Delta n = 10^13 cm^- 3 at x = 0 Delta p = Delta n = 0 at x < n T_n = T_p = 1 Mu s Delta n = 25 cm^2/s, Dp = 10 cm^2/s T = 300 degree k, V_T = 26 mv on injection, the change in minority carrier - Concentration is predominant by continuity equation, E = 0, G_L = 0 for x > 0 D_n partial differential^2 np/partial differential x^2 - n_p - n_p 0/T_n =