【Device Papers】Defect-modulation in α-Ga₂O₃ molecular beam epitaxial photodetector investigated through pulsed-light persistent-photoconductivity

      Researchers from the King Abdullah University of Science and Technology (KAUST) have published a dissertation titled "Defect-modulation in α-Ga₂O₃ molecular beam epitaxial photodetector investigated through pulsed-light persistent-photoconductivity" in APL Materials.

Abstract

      α-phase gallium oxide (Ga₂O₃) features a corundum crystal structure that closely matches the low-cost sapphire substrate commonly used in epitaxy, enabling researchers to perform precise and controllable Ga₂O₃ epitaxy. It thus offers an excellent material platform for the development of high-power devices and deep ultraviolet photodetectors (DUV-PDs). In this study, we altered the epitaxy properties of α-Ga₂O₃ grown on m-plane sapphire substrates by changing the growth parameters of oxide molecular beam epitaxy and demonstrated effective modulation of the oxygen vacancy (V_O) dependent persistent photoconductivity (PPC) behavior. This gave rise to a tunable paired-pulse facilitation (PPF) index in the fabricated α-Ga₂O₃-based DUV-PDs. Using α-Ga₂O₃ grown on bare m-plane sapphire at 500 °C as a benchmark (α-Ga₂O₃-500 °C), we effectively altered the V_O contribution by either increasing the growth temperature to 570 °C or introducing a step-graded α-(Al_xGa_1−x)₂O₃ buffer. Photoluminescence and x-ray photoelectron spectroscopy analyses verified the variations in V_O incorporation within α-Ga₂O₃ grown under different conditions. Finally, owing to the higher incorporation of V_O defects within the material, the DUV-PD fabricated based on the α-Ga₂O₃–500 °C sample exhibited the most pronounced PPC behavior, achieving a maximum PPF index of 143% under a −1 V bias—representing a regulation amplitude of 26.5% compared to the control devices. The dominant V_O defects in α-Ga₂O₃ and variable range hopping led to the PPC behavior observed in the fabricated devices. Our investigation highlights the feasibility of tunable PPC performance in α-Ga₂O₃-based devices for x-ray to DUV detection and solar-blind neuromorphic vision systems, potentially in harsh environments.

DOI：

https://doi.org/10.1063/5.0266366