Question

A $ p $ - $ n $ photodiode is made of a material with a band gap of $ 2.0 \,eV $ . The minimum frequency of the radiation that can be absorbed by the material is nearly

• A. $ 10 \times 10^{14}\,Hz $
• B. $ 5 \times 10^{14}\,Hz $
• C. $ 1 \times 10^{14}\,Hz $
• D. $ 20 \times 10^{14}\,Hz $

Answer 1

Answer: (B)

$p-n$ photodiode is a semiconductor diode that produces a significant current when illuminated. It is reversed biased but is operated below the breakdown voltage.
Energy of radiation $=$ band gap energy
ie, $h v=2.0 eV$
or $v=\frac{2.0 \times 1.6 \times 10^{-19}}{6.6 \times 10^{-34}}$
$\approx 5 \times 10^{14} Hz$