Question

Light of wavelength 6000 nm falls on a p-n junction photodiode. This photodiode is fabricated from a semiconductor with a band gap of 2.8 eV. Then, which of the following statement is true ?

• A. This wavelength is not detected by the photodode
• B. This wavelength is detected by the photodiode
• C. Light is reflected back completely
• D. None of the above

Answer 1

The correct option is A This wavelength is not detected by the photodode

Given, $E_g=2.8eV=2.8\times 16\times {10}^{-19}J$
$-4.48\times {10}^{-19}J$Also, $E=\frac{hc}{\lambda }$
$=\frac{6.62\times {10}^{-34}\times 3\times {10}^8}{600\times {10}^{-9}}J$
$=3.31\times {10}^{-19}J$
Since, $E<E_g$ this wavelength of radiation is not detected.