Impacts of oxygen source on band alignment of ALD Al2O3/(α-, ε-)Ga2O3 interface

Abstract

Al2O3 films were deposited on α- and ε-Ga2O3 films by atomic layer deposition (ALD) in different plasma oxygen source (H2O, O3, O2 plasma). The α- and ε-Ga2O3 films were epitaxially grown on sapphire substrates by mist chemical vapor deposition (Mist-CVD) and pulsed laser deposition (PLD), respectively. The epilayer characteristics were investigated by high resolution X-ray diffraction (HRXRD), atomic force microscope (AFM) and high resolution transmission electron microscopy (HRTEM). Furthermore, the energy band diagrams of Al2O3/α-Ga2O3 and Al2O3/ε-Ga2O3 were investigated by X-ray photoelectron spectroscopy (XPS). On the basis of Ga 3d and Al 2p core-level spectra as well as α- and ε-Ga2O3 valence band spectra, the energy band diagrams of Al2O3/α-Ga2O3 and Al2O3/ε-Ga2O3 interface were determined. And the conduction band offset of Al2O3/α-Ga2O3 interfaces were estimated to be 1.21/1.31/1.27 eV for oxidant of H2O, O3 and O2 plasma, respectively, while that of Al2O3/ε-Ga2O3 were 1.61/1.72/1.7 eV, the conduction band offsets of Al2O3 grown by O3 and O2 plasma were higher than those grown by H2O. And, the conduction band offsets of all samples were greater than 1 eV, indicating that Al2O3 grown by ALD can be used as gate dielectric in (α-, ε-) Ga2O3 power device.