(a) A GaAs semiconductor resistor is doped with acceptor impurities at a concentration of of Na = 10¹7cm 3. The cross-sectional area is 85μm². The current in the resistor is to be I = 20mA with 10V applied. Determine the required length of the device. (up -210 cm²/Vs; ni = 106 cm³ at 300K). (b) The hole concentration in p-type GaAs is given by p = p = 101 (1 cm³ for 0≤x≤L where L p=1061- = 10μm. The hole diffusion coefficient is 10 cm²/s. Calculate the hole diffusion current density at x= 5μm. [1 pt.] (c) Consider a compensated n-type Silicon (n=1.5x100 cm³) at T = 300K with a conductivity of σ = 16 (cm) and an acceptor doping concentration of 10¹7 cm³ and mobility is approximately 400 cm²/Vs. Determine the donor concentration. [1 pt.] (q = 1.602x10-1⁹C; k = 8.62x105 eV/K or 1.38x10-23 J/K; 1eV = 1.602x10-19J; h = 6.626x10-34J-s, m. 9.1x10-31 kg; c = 3.0x108 m/s; &₁ = 8.854x10-12 F/m)