GaAs metal-oxide-semiconductor push with molecular beam epitaxy Y2O3 – In comparison with atomic layer deposited Al2O3

In-situ molecular beam epitaxy (MBE) Y2O3 films 1–2nm thick were epitaxially grown on GaAs(001)−4×6 reconstructed surfaces. Despite a large lattice mismatch, the hetero-structure exhibits outstanding thermal stability to 900°C with excellent capacitance-voltage (C-V) characteristics. Low interfacial trap densities (Dit's) of (3–5)×1011eV−1cm−2 were obtained using the conductance method (G-V) without discernible peaks at the mid-gap. The frequency dispersion of the measured C-Vs of the Y2O3/GaAs(001) is ~4.6% for p-GaAs and ~12.4% for n-GaAs. In contrast, the atomic layer deposited Al2O3 on GaAs(001) shows large Dit with a peak at the mid-gap, large C-V frequency dispersion, and low thermal stability at temperatures higher than 600°C. Synchrotron radiation photoemission results show intactness of the interfacial structure in the MBE-Y2O3/GaAs, while removal of the surface As atoms is found in the ALD-Al2O3/GaAs system.