Question

What is the reason to operate photodiodes in reverse bias ? A p-n photodiode is fabricated from a semiconductor with a band gap of range of 2.5 to 2.8 eV Calculate the range of wavelengths of the radiation which can be detected by the photodiode. 

Answer 1

(i) The fractional increase in majority carries is much less than the fractional increase in minority carriers. Consequently, the fractional change due to the photo – effects on the minority carrier dominated reverse bias current is more easily measurable than the fractional change in the majority carrier dominated forward bias current. Hence, photodiodes are preferable used in the reverse bias condition for measuring light intensity.