Abstract
Ga <sub>2</sub> O <sub>3</sub> (Gd <sub>2</sub> O <sub>3</sub> ), a high κ gate dielectric, ultrahigh vacuum (UHV)-deposited on GaAs and InGaAs has unpinned the Fermi level in the high-electron-mobility III-V compound semiconductors for the first time. Systematic heat treatments under various gases and temperatures were studied to achieve low leakage currents of 10 <sup>- 8</sup> -10 <sup>- 9</sup> A/cm <sup>2</sup> and low interfacial density of states (D <sub>it'</sub> s) in the range of < 10 <sup>11</sup> cm <sup>- 2</sup> eV <sup>- 1</sup> . By removing moisture from the oxide, thermodynamic stability of the Ga <sub>2</sub> O <sub>3</sub> (Gd <sub>2</sub> O <sub>3</sub> )/GaAs heterostructures and the interfaces were achieved with high temperature annealing, the oxide remains amorphous and the interface remains intact with atomic smoothness and sharpness. The Fermi-level unpinning in atomic layer deposition (ALD) Al <sub>2</sub> O <sub>3</sub> ex-situ deposited on InGaAs was achieved. Recent work of extremely high-quality nano-thick single crystal oxides of gamma-Al <sub>2</sub> O <sub>3</sub> and bixbyite cubic Sc <sub>2</sub> O <sub>3</sub> epitaxially grown on Si (111) is discussed. Interfacial manipulation is essential in giving excellent results presented in the paper. X-ray diffraction, reflectivity, and X-ray photoelectron spectroscopy using synchrotron radiation are critical in probing the interfacial properties. © 2006 Elsevier B.V. All rights reserved.