Question

Why does a gradient occur in a semi-conductor?

(a) Because of current flow

(b) Because of diffusion current

(c) Because of drift current

(d) Because of difference in concentrations

The question was asked during an internship interview.

My query is from Drift and Diffusion Current in chapter Diode Circuit of Analog Circuits

Answer 1

The correct choice is (d) Because of difference in concentrations

The explanation: As there is a different level of doping in the p and n regions of a semi-conductor, the carriers (either holes or electrons) move from a region of high concentration to a region of low concentration giving rise to diffusion current.