Problem 2. [40 Points) A Gallium Arsenide semiconductor resistor at T=300 K is doped with Phosphorus with concentration of 1x10 cm. The cross sectional area is 20x10-6 cm. The current in the resistor is to be I=2mA with 20V applied. Answer the following questions: a) (10 Points] Determine the required length of the material if the mobility of electrons is assumed to be 8500 cm/V.s. b) (10 Points) Determine the required length of the material if the material is changed to Silicon with electron mobility equals 1400 cm?/V.s. c) [10 Points] Determine the required length of the material if the material is changed to Germanium with electron mobility equals 3900 cm/V.s. > d) (10 Points] Explain the reason of the differences among the results in parts a, band c