Question

A p – n photodiode is fabricated from a semiconductor with a band gap of $2.5$ eV. The signal wavelength is

• A. 6000 $\overset{o}{A}$
• B. 6000 nm
• C. 4000 nm
• D. 5000 $\overset{o}{A}$

Answer 1

Answer: (D)

5000 $\overset{o}{A}$

Answer 2

: the detection occurs only when the energy of incident photon greater than or equal to the energy band gap

$\frac{hc}{\lambda} = 2.5eV$

$\therefore\lambda = \frac{hc}{2.5eV} = \frac{1240eV}{2.5eV} = 496nm \approx 5000Å$