A p–n photodiode is made of a semiconductor with band gap 2.5 eV. It can detect light of which wavelength?
Options

Question

A p–n photodiode is made of a semiconductor with band gap 2.5 eV. It can detect light of which wavelength?

G1 Physics · Accepted Answer

Minimum photon energy for electron–hole generation ≈ E_g = 2.5 eV. Therefore longest detectable wavelength λ_max = 1240/2.5 = 496 nm = 4960 Å. Only 4000 Å (=400 nm) has greater photon energy than the gap. Final answer: Option D.