7) When light strikes a pure semiconductor such as silicon, electrons are promoted from a nearly lled valence band to a nearly empty conduction band. Conduction electrons produced by the light near the crystal surface diffuse as an ideal gas at 300 K and randomly drop back into the valence band with an average lifetime of 0 l s. a) Complete the table below to compare the electron gas with N 2 gas in air at 300 K, assuming a collision time (with phonons) of 0.01 ns. b) Calculate the average depth an electron diffuses from the crystal surface during its lifetime of l s. (Hint: Use the Equipartition Theorem for average velocity.) light crystal 0 \\L V\" '. uni Molecules 2 |500mfs | 0.2118 | 0.1 In |1.67 10-5m2fs gas electron l I 001 ns l