Question

A photodetector is made from a semiconductor In ${}_{0.53}Ga$${}_{0.47}As$ with $E_g$ = 0.73 eV. What is the maximum wavelength, which it can detect

• A. 1000 nm
• B. 1703 nm
• C. 500 nm
• D. 173 nm

Answer 1

The correct option is B 1703 nm

Limiting value of hv is $E_g$, such that hv = $\frac{hc}{\lambda }$ = $E_g$
or $\lambda =\frac{h_c}{E_g}=\frac{6.63\times {10}^{-34}J-s\times 3\times {10}^{8}m{s}^{-1}}{0.73\times 1.6\times {10}^{-19}J}$
= 1703 nm