Fabrication and Characterization of Amorphous GaOx Thin-Film UV-C Photodetectors on Quartz Glass Substrates

This study investigates amorphous gallium oxide (a-GaOx) thin-film UV-C photodetectors fabricated on synthetic amorphous quartz glass substrates using fine channel mist chemical vapor deposition (CVD) at 260°C. Post-deposition annealing (PDA) was performed at temperatures up to 800°C. X-ray diffraction confirmed that the films maintained their amorphous structure even after high-temperature PDA, in contrast to sapphire substrates, where crystallization and Al atom diffusion are typically observed. Optical measurements revealed that the optical bandgap (Eg,opt) remained nearly constant after PDA, indicating that the quartz substrates effectively suppressed bandgap widening. PDA significantly reduced the dark current by more than two orders of magnitude, enhanced the UV-C wavelength selectivity, and suppressed persistent photoconductivity by shortening the response time. Device performance metrics, including responsivity (R), detectivity (D*), external quantum efficiency (EQE), and photo-to-dark current ratio (PDCR), were markedly improved, with the best results obtained for films treated at 800°C. These findings highlight the efficacy of combining quartz substrates with PDA to realize high-performance a-GaOx UV-C photodetectors.