Gain and excess noise properties of 3-gain-stage InGaAs/InAlAs avalanche photodetector

-We constructed a model for a 3 -stage InGaAs/InAlAs avalanche photodiode using numerical simulations based on the gain -noise mechanism. The contact layer, barrier layer, charge layer and multiplication layer of this model are optimized accordingly. The performance of the device can be improved by optimizing the thickness and doping concentration of the contact layer, increasing the thickness of the charge layer, and adding a barrier layer. At the same time, the addition of double heterojunction structure makes the performance of the device better, which enables a higher impact ionization rate of the multiplication layer. According to DSMT theory calculation results, the optimized 3 -gain -stage device's gain is 90, and the excess noise factor is about 3.1. Compared with the 10 -stage avalanche photodiode (with an excess noise factor of 5) studied at the same gain, this work shows higher performance at the lower stage. The optimized structure can provide design and optimization ideas for more stages of avalanche photodiode to increase gain and reduce excess noise.