【Device Papers】Structural and Electronic Properties of β-(AlₓGa₁₋ₓ)₂O₃ Active Layers for Space-Qualified Solar-Blind Photodetectors

      Researchers from the University of Technology Sydney have published a dissertation titled "Structural and Electronic Properties of β-(Al_xGa_1–x)₂O₃ Active Layers for Space-Qualified Solar-Blind Photodetectors" in ACS Applied Electronic Materials.

Abstract

      This paper presents a detailed investigation of the structural, optical, and electronic properties of (Al_xGa_1–x)₂O₃ thin films used as active layers in solar-blind ultraviolet C (UVC) photodetectors onboard the INSPIRE-Sat 7 nanosatellite. Engineered via alloying Ga₂O₃ with Al₂O₃, these deep UV detectors exhibit a Gaussian spectral response centered at 215 nm with a full width at half maximum of 40 nm, enabling selective monitoring of solar irradiance in the Herzberg continuum (200–242 nm). The (Al_xGa_1–x)₂O₃ films are grown on c-plane sapphire substrates using pulsed laser deposition. Structural and optical analysis reveals that the engineered film exhibits the monoclinic β phase with a dominant (−201) orientation and the Al fraction of 0.58, inducing a 0.93 eV bandgap widening from 4.89 eV (Ga₂O₃) to 5.82 eV. Complementary photoemission and X-ray absorption spectroscopy studies reveal a 0.17 eV valence band downshift and a 0.74 eV conduction band uplift due to the alloying at x = 0.58. Cathodoluminescence spectroscopy identifies broad emission peaks at 3.55, 3.34, and 3.10 eV, attributed to self-trapped hole states localized at O sites adjacent to Al and Ga, respectively, and donor–acceptor pair recombination, consistent with the band structure modifications induced by Al₂O₃ alloying. These findings provide critical insights into β-(Al_0.58Ga_0.42)₂O₃ photodetector performance for Herzberg continuum detection in space applications.

DOI：

https://doi.org/10.1021/acsaelm.5c00794