Improved high-temperature device transport properties and off-state characteristics of AlGaN/GaN power devices with atomic layer deposition (ALD) HfAlO high-k dielectric

Abstract

The effect of the atomic layer deposition (ALD) HfAlO high-k dielectric on device transport properties and breakdown characteristics of an AlGaN/GaN metal–oxide–semiconductor hetero-junction field-effect transistor (MOS-HFET) was evaluated based on temperature-dependent measurements. It was found that the MOS-HFET device with a HfAlO gate dielectric shows high-channel mobility greater than the Schottky HFET device for the measured temperature range (25–150 °C). In the case of off-state breakdown characteristics, the MOS-HFET device greatly suppressed gate leakage currents for measured temperatures (25–200 °C) resulting in improvements in off-state breakdown characteristics. In contrast, large gate/drain leakage currents were observed for the Schottky HFET device at high temperature (>100 °C) resulting in about 200 V of breakdown voltage reduction. It was also found that the ALD HfAlO layer reduced surface leakage current by passivating the GaN surface effectively. Therefore, the MOS-HFET structure with the HfAlO gate dielectric is very attractive for GaN-based high-power and high-temperature device applications.