Why are photodiodes used preferably in reverse bias condition? A photodiode is fabricated from a semiconductor with band gap of 2.8 eV. Can it detect a wavelength of 6000 nm? Justify ?

Photodiodes are used in reverse bias as in reverse bias the depletion layer increases which results in decrease of junction capacitance and response time. Low response time is essential for a photodiode. Also the photocurrent is directly proportional to the illuminance .For photodiode to detect the incident wavelength , Band gap energy(2.8eV)