Properties of κ‐Ga₂O₃ Prepared by Epitaxial Lateral Overgrowth

The structural and electrical properties of undoped and Sn doped κ‐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 ≈ 10¹³ 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 °C increases the donor density near the surface to ≈ 10¹⁹ cm⁻³. Such samples show strong persistent photocapacitance and photoconductivity, indicating the possible DX‐like character of the centers involved. For thin (5 µm) κ‐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 κ‐Ga₂O₃/GaN interface.