Performance Study On Avalanche Photodiodes Based On Compound Semiconductor

In this paper,by establishing the model of compound semiconductor avalanche photodiode(APD),we studied the APD based on different semiconductor materials,simulated and optimized the device.Using Silvaco TCAD,the separate absorption,grading,charge,and multiplication(SAGCM)structure of InGaAs/InAlAs heterojunction APD,separate absorption and multiplication(SAM)structure of GaN APD,SAM structure of AlGaN APD,and modified SAM structure AlGaN APD are modeled and analyzed.First,by adjusting the devices' model and parameters,the dark current,photocurrent and gain characteristics of the device obtained by simulation have been fitted with the experimental results to ensure the reliability of devices' model.Then,the structure of the devices have been optimized,by changing the parameters of the devices,with formula calculation,the I-V characteristic,gain characteristics,energy band and the electric field of the devices have been analyzed.Details are as follows:(1)For the InGaAs/InAlAs heterojunction APD,with the increasing doping and thickness of charge layer,the punchthrough voltage decreased,and the breakdown voltage increased,the operating voltage range increased;Furthermore,the simulation shows that the doping and thickness of the multiplication layer can also affect the operating voltage range of the device,through the analysis of the I-V characteristic and the electric field,we get the optimized structure.(2)For GaN APD,through the simulation,the characteristics of the device have been analyzed by comparing the I-V characteristics,electric field distribution and gain with different structure parameters.(3)For the SAM structure of AlGaN APD,first,through the analysis of the device,we can observe that with the change of Al content of different layer,the performance of the device changed obviously;by optimizing the traditional SAM structure,analyzed the effect of multiplication layer parameters on the device,and after inserting an intermediate layer into the multiplication layer,the effect of intermediate layer on APD has been analyzed;furthermore,the charge layer has also been analyzed.