Question

The electrical conductivity of a semiconductor increases when electromagnetic radiation of a wavelength shorter than $2480 \, nm \,$ is incident on it. The bandgap (in $eV$ ) for the semiconductor is

• A. $0.9$
• B. $0.7$
• C. $0.5$
• D. $0.1$

Answer 1

Answer: (C)

Band gap is the energy gap between conduction and valence band

For excitation of $e^{-}$ from valence band to conduction band
$E_{phton}\geq E_{g}$
$\frac{hC}{\lambda }\geq E_{g}$
$\left(\text{E}\right)_{\text{g}} = \frac{\text{1240} \text{eV}}{\lambda \text{(nm)}}$
$\text{E}_{\text{g}} = \frac{\text{1240 eV}}{\text{2480 }} = \text{0.5 } \text{eV}$