Question

A $p$ - $n$ photodiode is made of a material with a band gap of $2.0eV$ . 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, $hv=2.0eV$
or $v=\frac{2.0\times 1.6\times 10^{-19}}{6.6\times 10^{-34}}$
$\approx 5\times 10^{14}Hz$