germanium is another elemental semiconductor material commonly used in single crystal form. If you have a germanium crystal that is 20 mm long, 1 mm wide, and 1 mm thick, and doped with 10¹⁶antimony atoms per cubic centimeter:

(a) calculate the conductivity of the germanium crystal. Assume the electron mobility is 3600 cm²V^-1sec^-1 and that each Sb atom contributes 1 electron for conduction.

(b)if the Sb-doped germanium is illuminated with 10¹⁴photons with sufficient energy to each produce a conduction electron, calculate the change in conductivity assuming each photon creates one conduction electron. Hint:recall that in the conductivity equation we used often in our discussions, the value of n is in terms of electrons per unit volume.