# An n-type GaAs is uniformly doped with Np = 2 x 1010 cm-3 concentration of donors. Voltage is applie

An n-type GaAs is uniformly doped with Np = 2 x 1010 cm-3 concentration of donors. Voltage is applied across a L= 100 um long piece of this GaAs crystal which leads to an electric potential V (x) inside the semiconductor that is given by, V (x) V where x is distance from one end of the semiconductor. Assume that the excess holes generated by the applied voltage is much greater than the excess electrons (Ap An). The intrinsic carrier density in GaAs is ni 1.8 x 106 cm-3. The diffusion constants for electrons and holes are Dr=220 cm2/s and Dp 10 cm2/s, respectively (a) Calculate the thermal equilibrium concentration of electrons (no) and holes (po). (10 points) (b) Determine the density of excess holes (Ap). (Hint: Use Poisson&#39;s equation to determine the total charge in the GaAs crystal generated by the applied voltage). (15 points) (c) Calculate the total conductivity of the GaAs crystal with the applied voltage. (10 points) (d) Determine the drift current density in the crystal at (a) x 0, (b) x = L/2, and (c) x = L. If you are not able to answer part (c), use o 35 uS/cm. (10 points)