Design and simulation of a high gain-bandwidth product InGaAs/AlGaAsSb avalanche photodiode with a p-type hybrid absorption layer.

The rapid development of optical communication has increased the demand for high-speed and high-sensitivity avalanche photodiodes (APDs). However, there is a well-known trade-off between the bandwidth and responsivity of the avalanche photodiodes. To solve this problem, we design and simulate an avalanche photodetector with highly doped, Gaussian-doped, and unintentionally doped hybrid absorption layers. The results show that the maximum 3 dB bandwidth of the optimized device increases from 20.1 to 28.1 GHz. At a gain of 20, the 3 dB bandwidth increases from 18.1 to 22.4 GHz, and the gain-bandwidth product experiences an increase of 86 GHz. The introduction of the Gaussian-doped region creates a gradually increasing electric field. Due to the effect of negative differential mobility in InGaAs, the electron drift velocity in this region is significantly increased. In addition, we also analyzed the influence of charge layer doping concentration on the APD bandwidth. The study indicates that reducing the doping concentration increases the bandwidth at low gain, while decreasing it at high gain. This research can provide a reference for the structural design of high-speed APDs.