Gan-based Pin Photodetector Structure Design And Optimization

The pin ultraviolet photodetector based on GaN material can be uesed for a plentyof applications such as missile plume detection, flame detection, and secure-from-earthinter-satellite communications, which attracts intense interest in many countries inrecent years.This paper analyzes the principles of the pin photodetector and establishs thephysical parameter models of GaN material. By solving the one-dimensional driftdiffusionequation, the analytical model of GaN-based pin photodetector is established.On the basis of the analytical model, we quantificationally calculate the photocurrent,the responsivity spectrum, as well as the photocurrent contribution of all various layers.Besides, we design two types of front-illustrated GaN-based pin photodetector:homostructure and heterostructure photodetectors. The p-layer of the photodetector hasgreat influence on the spectral response; hence, an effective way to improve the spectralresponse is to optimize the p-layer. For GaN/AlGaN/GaN heterojunction photodetector,UV/Solar injection ratio reduces with higher reverse voltage and UV/Solar injectionratio will increase up to 103, while effect of polarization and dipole is considered.UV/Solar injection ratio will increase significantly, after inserting a barrier enhancementlayer or InGaN quantum well.In addition, we design a solar-blind GaN-based back-illuminated pin photodetectorand analyze its physical mechanism. Width of p-layer and i-layer has been optimized tothe best theoretic values. After simulation and analysis, the responsivity changing withthe reverse bias is not attributed to the expansion of the depletion region, but to tworeasons as follows. (1) The effect of GaN/AlGaN heterojunction barrier to block theelectrons decreases for higher bias; (2) The recombination rate of excess carriersdecreases due to electric field increasing in depletion region. At zero bias, the simulatedresponsivity reaches its maximum 0.12A/W, with quantum efficiency 55.1%. Themeasured peak responsivity is more than 0.09A/W, with quantum efficiency greater than41.6%. Comparing the simulation with the experimental data, they are almost consistentwith each other.