Properties of -Ga₂O₃ Prepared by Epitaxial Lateral Overgrowth

The structural and electrical properties of undoped and Sn doped kappa-Ga2O3 layers grown by epitaxial lateral overgrowth on TiO2/sapphire substrates using stripe and point masks show that the crystalline structure of the films can be greatly improved relative to conventional planar growth. The undoped films are semi-insulating, with the Fermi level pinned near E-C-0.7 eV, and deep electron traps at E-C-0.5 eV and E-C-0.3 eV are detectable in thermally stimulated current and photoinduced current transient spectra measurements. Low concentration Sn doping results in net donor concentrations of approximate to 10(13) cm(-3), and deep trap spectra determined by electron traps at E-C-0.5 eV, and deep acceptors with an optical ionization threshold near 2 and 3.1 eV. Treatment of the samples in hydrogen plasma at 330 degrees C increases the donor density near the surface to approximate to 10(19) cm(-3). Such samples show strong persistent photocapacitance and photoconductivity, indicating the possible DX-like character of the centers involved. For thin (5 mu m) kappa-Ga2O3 films grown on GaN/sapphire templates, p-type-like behavior is unexpectedly observed in electrical properties and we discuss the possible formation of a 2D hole gas at the kappa-Ga2O3/GaN interface.