Question

A silicon PN junction diode under revers bias has depletion width of 10µm, relative permittivity is 11.7 and permittivity, ε0 =8.85×10^-12F/m. Then depletion capacitance /m^2 =?

(a) 0.1µF/m^2

(b) 1.7µF/m^2

(c) 10µF/m^2

(d) 0.5µF/m^2

This question was addressed to me in an interview.

The query is from Diode Capacitances topic in section Semiconductor-Diode Characteristics of Electronic Devices & Circuits

Answer 1

The correct option is (c) 10µF/m^2

Explanation: We know, CT =Aε0εr /W

CT/A= (8.85×10^-12)(11.7)/10

         =10

 By putting the values we get 10µF/m^2.