AlGaN/GaN HEMT DC Simulation

Abstract

Increasing demand in high power and high frequency semiconductor devices has promoted the rapid development of microwave power devices using GaN and SiC. Characteristics like high breakdown voltage and high electron mobility enable AlGaN/GaN HEMT the possibility to be utilized as high power RF devices. However, obstacles prevent the widely utilization of AlGaN/GaN transistor in this field. It has been generally recognized the superabundant trap density in GaN and AlGaN material limits the performance of the devices by bringing in reliability issues like current collapse and gate-lag. Lattice mismatch in GaN and AlGaN and abrupt heterojunction interface of AlGaN/GaN contribute to the unstable performance while high voltage is applied to drain contact which will cause high field between thin layer of AlGaN/GaN interface. An overall introduction to HEMT physics will be presented in chapter 2 of this work. Attention will be paid to the performance degradation analysis caused by issues such as trapping effect, self-heating, displacement damage and high voltage induced lattice mismatch. The chapter 3 of this work presents a process to use TCAD simulation tool to match the simulation results with measurements from real devices starting from building device structure. Adjustments of parameters including gate barrier height, electron mobility, polarization coefficients and parasitic resistance will be made to fit the measurements.