|dc.description.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.||en_US