Question

What makes up the total current in a semi-conductor?

(a) Only diffusion current

(b) Only drift current

(c) Drift+diffusion current

(d) Drift+diffusion+biasing current

I have been asked this question during an interview for a job.

My enquiry is from Drift and Diffusion Current in portion Diode Circuit of Analog Circuits

Answer 1

The correct choice is (c) Drift+diffusion current

To explain: In an unbiased semi-conductor the drift current is balanced by diffusion current and hence there is no current flowing in the semi-conductor in this condition, but in biased condition both these currents are unbalanced and hence the total current flowing is the vector sum of both drift and diffusion current.