A p-n photodiode is fabricated from a semiconductor with band gap of 2.8 eV. Can it detect a wavelength of 600 nm?

Solution

Given,
Energy band gap, E_g = 2.8 eV
Wavelength of the photon, $λ$ = 600 nm

Using the formula for energy of a photon,

$E = \frac{hc}{λ}$

we have, E $= \frac{6.6 \times 10^{- 34} \times 3 \times 10^{8}}{600 \times 10^{- 9} \times 1.6 \times 10^{- 19}} eV$

$= 2.06 eV < 2.8 eV (E_{g})$

As, E < E_g, so p-n junction cannot detect the radiation of given wavelength.