The energy of a photon of sodium light `(lambda=589 nm)`equal the band gap of a semiconducting material.(a)Find the minimum energy E requried to create a hole-electron pair.(b)Find the value of `E//kT`at a temperature of 300K.

Explanation

(a) `E=(hc)/(lambda)=(1242)/(589)=2.1eV`
(b) `(E)/(kT)=(2.1xx1.6xx10^(-19))/(1.38xx10^(-23)xx300)=81`
It is difficult for the thermal energy to create the hole-electron pair but a photon of light can do it easily.