Modeling of gallium nitride high electron mobility transistors

A Monte Carlo device simulator was developed to investigate the electronic transport properties in AlGaN/GaN High Electron Mobility Transistors (HEMTs). Two different polarization models were considered to introduce polarization effects at the interface and their effect on the device characteristics were compared. The influence of the gate-voltage dependence of the polarization charge on the electron sheet charge density in the channel was determined. We found that a 10% increase in the polarization charge is needed to match the experimental data when the gate voltage dependence of the polarization charge is included in the theoretical model. This information is important for calibration in commercial device simulators and for better understanding of the quality of the GaN/AlGaN interface.;Quantum corrections to the semi-classical charge description were included in the model via the use of the effective potential approach. Results generated using this Monte Carlo simulator that incorporates polarization effects and quantum corrections show good agreement with the experimental DC current---voltage characteristics.;The influence of thermal effects was also investigated to get a better understanding on the role of self-heating effects on the electrical characteristics of GaN HEMTs. This is implemented by solving simultaneously the acoustic and optical phonon energy balance equations and taking into account the coupling of the two subsystems. The electro-thermal device simulator was used to observe the temperature profiles across the device. Hot spots or regions of higher temperatures were found along the channel in drain end of the channel. The preliminary results from the electro-thermal simulations suggest that the thermal effects do not have drastic effect on the electrical characteristics of GaN HEMTs, the current reduction falls between 5--10% over the simulated range of voltages. However, the non-equilibrium phonon effects might play an important role in determining the thermal distribution in these HEMTs and thus, resulting in reliability issues such as current collapse.