Enhanced Responsivity of β-Ga2O3-Based Solar-Blind Ultraviolet Photodetectors via Inductively Coupled CF4 Plasma Treatment

Solar-blind photodetectors (SBPDs) based on β-gallium oxide (β-Ga2O3) are promising candidates for ultraviolet C (UVC) photodetection applications, owing to their ultrawide band gap and excellent stability; however, their performance is often limited by oxygen-vacancy-related defects and trap-assisted leakage processes arising from heteroepitaxial growth. In this work, we demonstrate a plasma-assisted interfacial engineering approach to enhance the performance of β-Ga2O3 SBPDs using CF4 plasma-treated c-plane sapphire substrates. CF4 plasma pretreatment modifies the sapphire surface prior to β-Ga2O3 growth, as evidenced by fluorine-related surface species on the treated substrate, altered surface wettability, and increased surface energy. These surface changes influence the nucleation behavior and interfacial evolution of subsequently grown β-Ga2O3 films. Structural and chemical analyses revealed improved crystalline quality, with the full width at half maximum (FWHM) of the β-Ga2O3 (-402) rocking curve reduced from 1.93° to 1.38°, along with a decreased oxygen-vacancy-related contribution from 27.8% to 25.3%. Metal-semiconductor-metal-structured SBPDs fabricated on the treated films exhibited significantly enhanced optoelectronic performance under 236 nm illumination, including suppressed dark current and increased responsivity. Moreover, their photocurrent-to-dark-current ratio reached 3.13 × 105, corresponding to an approximately 295-fold enhancement compared with that of the untreated devices, while the rise time decreased from 16.94 to 3.74 s. Additionally, the UV (236 nm)/visible (400 nm) rejection ratio increased from 1.58 × 103 to 5.19 × 105, indicating excellent UVC selectivity. In summary, this study reports a scalable and effective strategy for developing defect-modulated β-Ga2O3 SBPDs with improved responsivity, faster photoresponse, and strong solar-blind UVC selectivity.