The drift velocity acquired by a charge carrier in a unit electric field is called its electrical mobility and is denoted by μ. i.e. . Mobility of electrons in the VB is less than the mobility of electrons in the CB.
Current in a SC is, I = [ve ne + vh nh] e
Conductivity of SC is, σ = e [ne μe + nh μh],
σSi = 10–11 σCu = 10+13sfused quartz
Due to very small number density of charge carriers the conductivity of intrinsic SCs is very low & they are of no practical utility.