Yurui Han, Zijin Lu, Weizhe Cui, Jiale Zhang, Xinjian Ma, Youheng Song, Yichun Liu, Bingsheng Li, Yuefei Wang, Rongpeng Fu, Aidong Shen, Yujie Wang
(AlxGa1-x)2O3 alloy thin films with the tuning band gap in a range of 4.9 eV to 6.26 eV have been achieved by adjusting the Al composition (x ≈ 0-0.77) grown on a c-plane sapphire substrate via Metal-Organic Chemical Vapor Deposition (MOCVD), with the increase of band gap, the fabricated metal-semiconductor-metal (MSM) photodetectors achieved a systematic extension of their spectral response range, covering from deep ultraviolet (250 nm) to vacuum ultraviolet (198 nm) wavelengths. XRD characterization results indicated that the crystal structure of the films transformed from a single monoclinic β-phase (x{less than or equal to}0.57) to a β/γ dual-phase coexistence state (x~0.67-0.77) with the increase in Al composition. The optimal surface morphology and crystalline quality of the films were obtained at an Al composition of 0.20. XPS analysis indicated that the V₀ defect concentration exhibited a trend of first decreasing and then increasing with the increase in Al composition, based on which the evolution law of V₀ defects was elucidated, and the intrinsic correlation between V₀ defects, lattice stress, phase transition and thin film crystalline quality was investigated. The fabricated MSM photodetectors exhibited excellent comprehensive performance at an applied bias of 10 V, with a dark current below 10 fA, a maximum specific detectivity of 6.58×1014 Jones and an ultrahigh UV-visible rejection ratio of 9.07×107. Under 185 nm illumination, the photodetector with a high Al composition (x=0.77) maintained a photocurrent-to-dark-current ratio of approximately 1.18×102, indicating its excellent detection sensitivity and anti-interference capability in the deep ultraviolet to vacuum ultraviolet wavebands.