Question

A p – n photodiode is made of a material with band gap of 2 eV. The minimum frequency of the radiation that can be absorbed by the material is nearly

(Take hc = 1240 eV nm)

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

Answer 1

Answer: (D)

$5 \times 10^{14}Hz$

Answer 2

: Here, $E_{g} = 2eV$

Wavelength of radiation corresponding to this energy is

$\lambda = \frac{hc}{E_{g}} = \frac{1240eVnm}{2eV} = 620nm$

Frequency$\upsilon = \frac{c}{\lambda} = \frac{3 \times 10^{8}ms^{- 1}}{620 \times 10^{- 9}m} = 5 \times 10^{14}Hz$