Characteristics of SiO2/n-GaN interfaces with β-Ga2O3 interlayers

We report on the characteristics of SiO2/n-GaN metal-oxide-semiconductor (MOS) structures with β-Ga2O3 interlayers. β-Ga2O3 15 nm thick was grown by dry oxidation at 800 °C for 6 h, and 100-nm-thick SiO2 was then deposited by sputtering. Capacitance–voltage measurements show a low interface trap density of ∼3.9×1010 eV−1 cm−2, probably indicating an unpinning of the surface Fermi level. Additionally, current–voltage measurements display a low leakage current of ∼1.2 μA/cm2 at a gate voltage of +20 V, regardless of rough oxide surface, as confirmed by atomic force microscopy observations. Thus, the stacked SiO2/β-Ga2O3 insulator is found to improve both the electrical interface properties and the gate dielectric characteristics of the GaN MOS structures.