Question

The delay in switching between the ON and OFF states is due to _________

(a) The time required to change amount of excess minority carriers stored in quasi-neutral regions

(b) The time required to change amount of excess majority carriers stored in quasi-neutral regions

(c) The conduction between storage time and recovery time

(d) The exponential increase in carriers in N region

I had been asked this question in a job interview.

This intriguing question comes from PN Diode Switching Times topic in chapter Semiconductor-Diode Characteristics of Electronic Devices & Circuits

Answer 1

Right answer is (a) The time required to change amount of excess minority carriers stored in quasi-neutral regions

Easiest explanation: When switched instantaneously it stays in a quasi state i.e.., temporary state which stores charges. The delay is produced due to this charge settlement. The diode needs to discharge these excess carriers in order to return the non conduction stage.