Question

A `p-n` photodiode is fabricated from a semiconductor with a band gap of `2.5 eV`. It can detect a signal of wavelength
A. 6000 Å
B. 6000 nm
C. 4000 nm
D. 5000 Å

Answer 1

Correct Answer - D
The detection occurs only when the energy of incident photon greater than or equal to the energy band gap
`(hc)/lambda=2.5 eV`
`therefore lambda=(hc)/(2.5 eV)=(1240 eV)/(2.5 eV)=496 nm ~~ 5000 Å`