Low Subthreshold Slope AlGaN/GaN MOS-HEMT with Spike-Annealed HfO₂ Gate Dielectric

AlGaN/GaN metal-oxide semiconductor high electron mobility transistors (MOS-HEMTs) with undoped ferroelectric HfO₂ have been investigated. Annealing is often a critical step for improving the quality of as-deposited amorphous gate oxides. Thermal treatment of HfO₂ gate dielectric, however, is known to degrade the oxide/nitride interface due to the formation of Ga-containing oxide. In this work, the undoped HfO₂ gate dielectric was spike-annealed at 600 °C after the film was deposited by atomic layer deposition to improve the ferroelectricity without degrading the interface. As a result, the subthreshold slope of AlGaN/GaN MOS-HEMTs close to 60 mV/dec and on/off ratio>10⁹ were achieved. These results suggest optimizing the HfO₂/nitride interface can be a critical step towards a low-loss high-power switching device.