Implementing κ-Ga2O3 Polymorphs Using Ga Predeposition

Single kappa-phase gallium oxide (κ-Ga2O3) has limited growth at low temperatures due to lattice constant mismatch with sapphire substrates. This study reports that gallium (Ga) predeposition effectively mitigates this mismatch, enabling the growth of κ-Ga2O3 epilayers at low temperatures rather than the more common α-Ga2O3 epilayers. High-resolution X-ray diffraction demonstrated that the Ga2O3 phase can be grown as pure α and κ-phases without the formation of mixed phases by controlling the gallium monochloride (GaCl) flow rate. Single κ-phase and mixed phases Ga2O3 samples for the structural and optical properties were analyzed. Furthermore, a deep ultraviolet photodetector device with a metal–semiconductor–metal structure was fabricated using κ-Ga2O3 thin films and lattice mismatch relaxation Ga predeposition layers grown at low temperatures. The device exhibited a sharp response with a maximum responsivity at 260 nm, indicating the potential of the grown κ-Ga2O3 as a highly selective ultraviolet C-band detector.