Extremely low excess noise and high sensitivity AlAs0.56Sb0.44 avalanche photodiodes

Fast, sensitive avalanche photodiodes (APDs) are required for applications such as high-speed data communications and light detection and ranging (LIDAR) systems. Unfortunately, the InP and InAlAs used as the gain material in these APDs have similar electron and hole impact ionization coefficients (α and β, respectively) at high electric fields, giving rise to relatively high excess noise and limiting their sensitivity and gain bandwidth product1. Here, we report extremely low excess noise in an AlAs0.56Sb0.44 lattice matched to InP. A deduced β/α ratio as low as 0.005 with an avalanche region of 1,550 nm is close to the theoretical minimum and is significantly smaller than that of silicon, with modelling suggesting that vertically illuminated APDs with a sensitivity of −25.7 dBm at a bit error rate of 1 × 10−12 at 25 Gb s−1 and 1,550 nm can be realized. These findings could yield a new breed of high-performance receivers for applications in networking and sensing.