Development of high-power, High Electron Mobility Transistors (HEMTs) has seen a major leap forward in recent years. In order to fully explore the potential of the devices, accurate simulation models are needed. We employ a Monte Carlo technique to investigate stationary electron transport in GaN and InN. The simulation results are used as a basis for the development of analytical models suitable for the simulation of GaN and InN-based electron devices.
We analyze different structures such as single and double heterojunction AlGaN/GaN HEMTs, as well as novel InAlN/GaN transistors. The latter provide higher polarization charges without the drawback of high strain, thus performance superior to AlGaN/GaN structures is predicted.
Our work also includes the optimization of various applications (high-power, high-frequency or high-breakdown), involving various enhancement techniques. We assess the impact of different effects such as thermionic field emission and self-heating on device performance. Studies are also conducted at elevated ambient temperatures. Since the longitudinal electric fields in the channel exhibit rather large values, we employ a hydrodynamic transport model.
Due to the intense interest in normally-off devices, several approaches are currently being analyzed. One such approach is the addition of an InGaN cap layer, which raises the conduction band of the AlGaN/GaN interface. Another approach is the recessed-gate technique, which also improves the RF performance. By exploring different mobility models, we have achieved good predictive results for RF transconductance, capacitances and cut-off frequency for devices of different technologies and geometries.
High electric power inverters are needed for the hybrid electric vehicles that have entered the market over the last couple of years. For such automotive applications, high breakdown voltage as well as low on-resistance and the capability to operate at high temperatures are key requirements. Our calibrated simulator is suitable for the design and optimization of such devices.