Study of GaN MOS-HEMT using ultrathin Al2O3 dielectric grown by atomic layer deposition

We report on a GaN metal-oxide-semiconductor high electron mobility transistor (MOS-HEMT) using atomic-layer deposited (ALD) Al2O3 as the gate dielectric. Through further decreasing the thickness of the gate oxide to 3.5 nm and optimizing the device fabrication process, a device with maximum transconductance of 150 mS/mm was produced. The drain current of this 0.8 μm gate-length MOS-HEMT could reach 800 mA/mm at +3.0 V gate bias. Compared to a conventional AlGaN/GaN HEMT of similar design, better interface property, lower leakage current, and smaller capacitance-voltage (C-V) hysteresis were obtained, and the superiority of this MOS-HEMT device structure with ALD Al2O3 gate dielectric was exhibited.