Ultrawide-bandgap AlGaN-based HEMTs for high-power switching

Abstract

The potential of AlGaN-based ultrawide-bandgap high-electron-mobility transistors (HEMTs) with high (> 60%) Al composition for use in high-power switching applications is studied. The devices are simulated with a gate length of 2 µm, and their figures of merit are evaluated as functions of the gate-to-drain distance, operating temperature, and different substrates. At room temperature (RT), the maximum drain current, ID (at a gate voltage of VGS = 2 V), ION/IOFF ratio, threshold voltage, and subthreshold swing are found to be 219 mA/mm, ~ 109, −11.4 V, and 85 mV/decade, respectively, at a drain bias of VDS of 15 V for the device with LGD = 3.5 µm. The breakdown voltages are calculated as 396–830 V for the devices with gate-to-drain spacing LGD varying from 3.5 to 9.5 µm, respectively. The lowest OFF-state power dissipation of 0.73 nW/mm is found for the device with LGD = 3.5 µm at RT. The device also shows excellent behavior at high temperatures. The high-Al-content AlGaN-based HEMT with an AlN/sapphire substrate shows outstanding thermal stability and exhibits little thermal droop at high voltages. These results indicate that the structure proposed herein is an excellent choice for high-power switching devices.