Question

A semiconductor has acceptor levels \(57 \, \text{meV}\) above the valence band. The maximum wavelength of light which can excite an electron is:

• A. \(2.18 \times 10^{-4} \, \text{m}\)
• B. \(4.18 \times 10^{-4} \, \text{m}\)
• C. \(6.18 \times 10^{-4} \, \text{m}\)
• D. \(8.18 \times 10^{-4} \, \text{m}\)

Hint:

Convert energy from meV to joules using 1 eV = 1.6 × 10−19 J before calculating wave-length.

Answer 1

The Correct Option is A

The wavelength is given by:
\[\lambda = \frac{hc}{E}\]
Substitute $E = 57 \text{ meV} = 57 \times 10^{-3} \times 1.6 \times 10^{-19} \text{ J}$:
\[\lambda = \frac{6.626 \times 10^{-34} \times 3 \times 10^{8}}{57 \times 10^{-3} \times 1.6 \times 10^{-19}} \approx 2.18 \times 10^{-6} \text{ m}\]