Semiconductor Electronics Materials Devices and Simple Circuits - Result Question 22
22. A $p-n$ photodiode is fabricated from a semiconductor with a band gap of $2.5 eV$. It can detect a signal of wavelength
(a) $4000 nm$
(c) $4000 \AA$
(b) $6000 nm$
(d) $6000 \AA$
[2009]
Show Answer
Answer:
Correct Answer: 22. (c)
Solution:
- (c) $\lambda _{\max }=\frac{hc}{E}$
$=\frac{6.6 \times 10^{-34} \times 3 \times 10^{8}}{2.5 \times 1.6 \times 10^{-19}} \simeq 5000 \AA$
The wavelength detected by photodiode should be less than $\lambda _{\max }$. Hence it can detect a signal of wavelength $4000 \AA$.
