Ni/Au–Al2O3 gate stack prepared by low-temperature ALD and lift-off for MOS HEMTs

Abstract

We present the technology and performance of AlGaN/GaN MOS HEMTs with Al2O3 gate insulation. Definition of the Ni/Au gate metallization and underlying Al2O3 into a gate stack was realized by a single photolithographic step and lifted-off. 10nm thick Al2O3 layers were deposited by the low-temperature (100°C) atomic layer deposition (ALD), using ALD processes with (PA) and without (T) remote plasma enhancement. A dielectric constant of as deposited Al2O3 εr∼7.5 was determined from C–V measurements. The MOS HEMTs properties were evaluated from I–V, and C–V measurements, and the PA and T modes for the ALD deposition of Al2O3 in the gate stacks were compared also after consecutive annealing/passivation steps.