Design considerations for In0.52Al0.48As based avalanche photodiodes

We provide a set of design considerations for In_0.52Al_0.48As based avalanche photodiodes (APDs) in an attempt to reduce the excess noise factor. We compared the effects of tapered electric fields to constant electric fields, in APDs with avalanche regions of 0.2 mum and 2.0 mum, on multiplication and excess noise factors using a Simple Monte Carlo model. We found that diodes having p⁺-n-n⁺ doping profiles produce the lowest and highest excess noise in diodes with avalanche regions of 0.2 mum and 2.0 mum respectively. However due to the higher peak electric fields in thin diodes with field gradients causing tunneling current to become significant, the ideal p⁺-i-n⁺ diodes still provide the overall preferred structure. We also observed that different electric field gradients in the p⁺ cladding regions have negligible effect on the excess noise factors.