Question

For which type of material, the number of free electron concentration is equal to the number of donor atoms?

(a) P type semiconductor

(b) Metal

(c) N-type semiconductor

(d) Insulator

This question was addressed to me in a job interview.

My question is from Charge Densities in a Semiconductor impurities in division Conduction in Semiconductors of Electronic Devices & Circuits

Answer 1

Right answer is (c) N-type semiconductor

Easiest explanation: The n-type semiconductor has equal concentration of free electron and donor atoms.