Modeling dislocation-related reverse bias leakage in GaN p-n diodes

Abstract

Finite element analysis software was used to model and visualize two p-n junction models: one with a single threading dislocation (TD) and a control without one. TDs are modeled as a Gaussian distribution of trap states with a full width at half maximum value of 5 nm localized around the r = 0 line in a cylindrical coordination such that the linear trap state density was 1 trap c-1-translation; this model allows the cylindrical symmetry of the c-plane GaN crystal orientation to be used to avoid more computationally intensive 3D models. In this work, a vertical p-n diode with typical doping characteristics and an equivalent threading dislocation density of 108 cm2 was modeled in reverse bias. Our simulations show that the dislocation-mediated leakage mechanism for reverse bias leakage in GaN p-n diodes is the generation of electron-hole pairs via a trap-assisted tunneling mechanism whereby electrons from the valence band use the intermediate trap state to traverse the band gap. This mechanism results in electron-hole pairs that are swept out of the junction by the reverse bias electric field. This behavior results in a measurable leakage current within the model with behavior consistent with experimental values. ? 2021 IOP Publishing Ltd.