What is the reason to operate photodiodes in reverse bias? A p-n photodiode is fabricated from a semiconductor with a bandgap of range of 2·5 to 2·8 eV. Calculate the range of wavelengths of the radiation which can be detected by the photodiode.

 

Answers (1)
S safeer

The change in current with the change in intensity of light is more significant in reverse bias condition.

Now, calculating the range of wavelength:-

We know,

\lambda =\frac{hc}{E }\; \; \; \; \; \; \; \; \; \; \left [ \because h=6.63\times 10^{-34},c = 3\times 10^{8}\right ]

Then,

\lambda_{1} =\frac{6.63\times 10^{-34} \times 3\times 10^{8}}{2.8\times 1.6\times 10^{-19}}=497\times 10^{-9}m

\lambda_{2} =\frac{6.63\times 10^{-34} \times 3\times 10^{8}}{2.5\times 1.6\times 10^{-19}}=444\times 10^{-9}m

Hence, the range of wavelengths of the radiation which can be detected by the photodiode is 444\times 10^{-9}m to 497\times 10^{-9}m.

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