Question

If the ratio of the concentration of electrons to that of holes in a semiconductor is 7/5 and the ratio of currents is Then, the ratio of their drift velocities is  

(a) 4/7

(b) 4/5

(c) 5/8

(d) 5/4

Answer 1

Correct option(d) 5/4  

Explanation:

The current flowing through a semiconductor is given as:

I = neAv_d 

where, 

I = current flowing 

n = number of electrons 

e = charge of an electron 

A = cross sectional area of semiconductor vd = drift velocity

Current flowing due to holes( I_h ) = en_h Av_h

Current flowing due to electrons = en_e Av_e

Required ratio: