Multiplication Noise Characterization of InAlAs-APD With Heterojunction

The excess noise and ionization coefficient ratio of InAlAs avalanche photodiodes (APDs) with heterojunctions has been measured. To obtain these values accurately, we used a differential amplifier and determined the optical current at which the avalanche multiplication equals 1. These made it possible to conduct measurements on excess noise including that in the low multiplication region. Measured ionization coefficient ratios at M=10 were 0.18 and 0.17 with multiplication layer widths of 0.2 and 0.7 ??m , respectively. Excess noise was reduced with an increase in the optical input power. This tendency appeared more prominently in APDs with a thin multiplication layer.