Electrical properties and interface abruptness of AlSiO gate dielectric grown on 0001¯ N-polar and (0001) Ga-polar GaN

Abstract

The electrical properties and the interface abruptness of aluminum silicon oxide (AlSiO) dielectric grown in situ on 0001¯ N-polar and (0001) Ga-polar GaN by metal organic chemical vapor deposition were studied by means of capacitance-voltage (CV) and atom probe tomography (APT) measurements. The growth of AlSiO on N-polar GaN resulted in a positive flatband voltage shift of 2.27 V with respect to that on Ga-polar GaN, which exemplifies the influence of the GaN surface polarization charge on the electrical properties of GaN-based metal oxide semiconductor (MOS) devices. The AlSiO/GaN(N-polar) interface was sharp, which resulted in nondispersive CV characteristics and a relatively low density of interface states (Dit) of 1.48 × 1012 cm−2. An intermixed layer of AlGaSiO was present at the interface between AlSiO and Ga-polar GaN, which contributed to the measured dispersive CV characteristics and resulted in an ∼2× higher Dit than that on N-polar GaN. The superior properties of the N-polar AlSiO MOS devices are promising for further advancement of N-polar GaN-based high electron mobility transistors for high-frequency and power electronics applications.