Sputtered N-doped (Al,Zr,Ti,Ta,Hf)Ox dielectric layers for high-performance thin-film transistor-based UV photodetectors

Although high-entropy materials (HEMs) show considerable promise for dielectric applications, few studies have been conducted on HEM-based thin-film transistors (TFTs). This study reports the radio-frequency sputtering fabrication of N-doped-(Al,Zr,Ti,Ta,Hf)O_x dielectric and ZnSnO channel-based TFTs for a high-performance ultraviolet (UV) detector. Various screening techniques and forming gas annealing conditions were employed to improve the quality of N-doped-(Al,Zr,Ti,Ta,Hf)O_x-dielectric films and reduce film defects. The optimal N-doped-(Al,Zr,Ti,Ta,Hf)O_x-dielectric films exhibited excellent dielectric properties, with high dielectric constant (high-k) values of approximately 68 and a low dielectric loss of 0.015 across a wide frequency range. The resulting device exhibited excellent performance with a threshold voltage of 0.15 V, on/off ratio of 5 × 10⁸, subthreshold swing of 0.065 V·dec⁻¹, and saturated mobility of 49.27 cm²·V⁻¹·s⁻¹. The TFT also exhibited remarkable long-term operational stability for up to six months and great stable performance under various gate bias stresses. The resulting TFT-based UV detector exhibited ultrahigh sensitivity of 9.04 × 10⁶, high responsivity of 8835 A·W⁻¹, detectivity of 7.76 × 10¹⁵ Jones, and external quantum efficiency of 4.3 × 10^6% under 253 nm UV illumination. Our findings highlight the significant potential of N-doped-(Al,Zr,Ti,Ta,Hf)O_x for next-generation electronic devices.