Consider a situation in which reverse biased current of a particular $\mathrm{P}-\mathrm{N}$ junction increase when it is exposed to a light of wavelength $\leq 621 \mathrm{~nm}$. During this process, enhancement in carrier concentration takes place due to generation of hole - electron pairs. The value of band gap is nearly.

JEE Main · 2021 · 22 Jul 2021 · Shift 2 · Modern Physics

Consider a situation in which reverse biased current of a particular

P - N

junction increase when it is exposed to a light of wavelength

\leq 621 nm

. During this process, enhancement in carrier concentration takes place due to generation of hole - electron pairs. The value of band gap is nearly.

(A)1 eV
(B)4 eV
(C)0.5 eV
(D)2 eV✓ Correct

Answer: (D)

Solution

The reverse current rises only when the absorbed photons can lift an electron across the gap, so the longest wavelength that still generates electron-hole pairs carries exactly the band gap energy.

E_{g} = \frac{h c}{λ} = \frac{1240 eV nm}{621 nm}

The band gap is nearly

2

eV.

JEE Main · 2021 · 22 Jul 2021 · Shift 2 · Single correct option

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