Low-temperature (600 °C) formation of Al2O3/ β -Ga2O3 interface with low interface state density employing substrate-surface O3 treatment processes

The benefit of employing O3 surface treatment of the β-Ga2O3 substrate to fabricate metal–oxide–semiconductor (MOS) capacitors with atomic-layer-deposited (ALD) Al2O3 as dielectrics was investigated systematically to design a fabrication process at a sufficiently low temperature (600 °C) which is expected to avoid high-temperature-induced deterioration of the electrical characteristics of the β-Ga2O3 substrate. With a post-deposition annealing (PDA) at 600 °C, the MOS interface characteristics with low interface state density (Dit) were achieved by performing O3 surface treatment at 300 °C prior to deposition of Al2O3 and/or by using O3 as the oxidant in ALD. The impact of the gas composition of the 600 °C PDA ambient for the stack fabricated with the above O3 treatments was further investigated to reduce Dit down to ∼2 × 1010 eV−1 cm−2 at an energy level of 0.2 eV below the conduction band edge.