Study of lowering onset gain for a high-speed InGaAs/InAlAs avalanche photodiode

We investigate a novel InAlAs avalanche photodiode with double p-field control layers, which effectively eliminates the potential barrier between InGaAs absorption and InAlAs avalanche layers. The fabricated APD exhibits a low onset gain required for future optical fiber communications systems. A large 3-dB bandwidth of 22 GHz is maintained with a low gain of 2.8 for an APD with 100-nm avalanche-layer, and a GB product of 235 GHz is also achieved.