Fabrication and Characteristics of AlInN/AlN/GaN MOS-HEMTs with Ultra-Thin Atomic Layer Deposited Al2O3 Gate Dielectric

Abstract

Al 0.85In0.15N/AlN/GaNmetal-oxide-semiconductor high electron mobility transistors (MOS-HEMTs) employing a 3-nm ultra-thin atomic-layer deposited (ALD) Al2O3 gate dielectric layer are reported. Devices with 0.6μm gate lengths exhibit an improved maximum drain current density of 1227mA/mm at a gate bias of 3 V, a peak transconductance of 328mS/mm, a cutoff frequency fT of 16 GHz, a maximum frequency of oscillation fmax of 45 GHz, as well as significant gate leakage suppression in both reverse and forward directions, compared with the conventional Al0.85In 0.15N/AlN/GaN HEMT. Negligible C — V hysteresis, together with a smaller pinch-off voltage shift, is observed, demonstrating few bulk traps in the dielectric and high quality of the Al2O3/AlInN interface. It is most notable that not only the transconductance profile of the MOS-HEMT is almost the same as that of the conventional HEMT with a negative shift, but also the peak transconductance of the MOS-HEMT is increased slightly. It is an exciting improvement in the transconductance performance.