I have simulated a p-i-n photodiode in Si, which has a large intrinsic region width, to capture a broad range of wavelengths from 400 nm to 900 nm. I see that the spectral response peaks at about 625 nm. I am interested to know why this happens at this wavelength?
I would expect the curve to decrease from the lower to the higher wavelengths, due to decreasing absorption coefficient values. Or is there something that I am missing here? Thanks for any clue!
For PIN photodiode the recombination of photogenerated carriers in Regions P ANODE and N CATHODE , reduces the internal quantum efficiency. if the N cathode is illuminated , N cathode the carrier lifetime is reduced considerably because of the high doping. This reduces the internal quantum efficiency for short wavelengths. The recombination of photogenerated carriers in region N is not very important for long wavelengths due to the small portion of photogenerated carriers in region N because of its large penetration depth. Light with long wavelengths penetrates deep into silicon substrate P (ANODE) and the recombination can reduce the internal quantum efficiency.
