An electric field us applied to a semiconductor.Let the number of charge carriers be n and the average drift speed be v.If the temperature is increased,

Options

A. both n and v will increase
B. n will increase but v will decrease
C. v will increase but n will decrease
D. both n and v will decrease

Answer

B

Explanation

When we increase the temperature, then more charge carriers are produced due to the breaking of covlent bands & average drift speed `[(v_d)_("evg")]` decreases with temperature due to increase of `v_(rms)` & decrease of relaxation time `tau`.
`(vecv_d)_(av) = - ((e tau)/m)vecE & tau = lambda/(v_(rms))`
where `lembda` is mean free path, `v_(rms) = sqrt((3kT)/m)`