Semiconductors Question 2
Question 2 - 2024 (01 Feb Shift 2)
Conductivity of a photodiode starts changing only if the wavelength of incident light is less than $660 \mathrm{~nm}$. The band gap of photodiode is found to be $\left(\frac{X}{8}\right) \mathrm{eV}$. The value of $\mathrm{X}$ is ;
(Given, $\mathrm{h}=6.6 \times 10^{-34} \mathrm{Js}, \mathrm{e}=1.6 \times 10^{-19} \mathrm{C}$ )
(1) 15
(2) 11
(3) 13
(4) 21
Show Answer
Answer: (1)
Solution:
$\mathrm{E}_{\mathrm{g}}=\frac{\mathrm{hc}}{\lambda}=\frac{6.6 \times 10^{-34} \times 3 \times 10^{8}}{660 \times 10^{-9}} \mathrm{~J}$
$=\frac{6.6 \times 10^{-34} \times 3 \times 10^{8}}{660 \times 10^{-9} \times 1.6 \times 10^{-19}} \mathrm{eV}$
$=\frac{15}{8} \mathrm{eV}$
So $\mathrm{x}=15$
