Numerical Simulation of Enhanced-Reliability Filleted-Gate AlGaN/GaN HEMT

Abstract

Reliability has been one of the major concerns for AlGaN/GaN high-electron-mobility transistors (HEMTs) over the past decades owing to their high-power operation. Although significant progress has been made in recent years, to position AlGaN/GaN HEMT technology as a disruptive technology, better understanding of reliability phenomena and their enhancement is necessary. Greater strength of physical phenomena such as converse piezoelectric strain, electric field, electron temperature, and Joule heating accelerates the degradation and reduces the lifespan of such devices. A detailed numerical study has been carried out to observe the impact of gate filleting on the performance of a AlGaN/GaN HEMT. It is observed that the converse piezoelectric strain in the AlGaN barrier layer, as well as the electron and lattice temperatures are suppressed due to the filleting of the gate geometry. To understand this more deeply, a comparison is drawn between field-plate rectangular-gate HEMTs and filleted-gate HEMTs with and without a field plate. For the filleted-gate HEMTs with and without a field plate, the electric field and converse piezoelectric strain are lower by 38% and 30%, respectively, as compared with the rectangular-gate HEMT with a field plate. As the filleting radius is increased, the gate leakage current and lattice temperature at the gate/AlGaN interface are reduced and the OFF-state reliability is enhanced, together with a reduction in the converse piezoelectric strain and electron temperature. Based on the presented analysis, a filleted-gate HEMT is proposed as a potential candidate to mitigate damage induced by converse piezoelectric strain, electron temperature, and Joule heating in future AlGaN/GaN-based high-power devices.