New GaN power electronics are being developed for power conversion and delivery. In electric transportation such as Electric and Hybrid Electric Vehicles (EV and HEV), these devices are becoming increasingly important and device cost and efficiencies are critical for their success. The high mobility and breakdown voltage of GaN make it an ideal material for power devices.
In particular, the 2D electron gas occurring at the AlGaN/GaN interfaces allows for very effective devices. However, the AlGaN layer requires a negative voltage on the gate to turn off. Such “D-mode” or “normally-on” devices do not meet fail-safe design criteria and therefore there is a strong drive to develop “E-mode” or “normally-off” devices.
There are several strategies to create such devices and using recess etching of the AlGaN barrier is a prominent one. Furthermore, gate dielectric layers are desired to limit leakage currents.