Flexible UV detectors based on in-situ hydrogen doped amorphous Ga₂O₃ with high photo-to-dark current ratio

Amorphous Ga₂O₃ (a-Ga₂O₃) has been attracting more and more attention due to its unique merits such as wide bandgap (4.9 eV), low growth temperature, large-scale uniformity, low cost and energy efficient, making it a powerful competitor in flexible deep ultraviolet (UV) photodetection. Although the responsivity of the ever-reported a-Ga₂O₃ UV photodetectors (PDs) is usually in the level of hundreds of A/W, it is often accompanied by a large dark current due to the presence of abundant oxygen vacancy (V_O) defects, which severely limits the possibility to detect weak signals and achieve versatile applications. In this work, the V_O defects in a-Ga₂O₃ thin films are successfully passivated by in-situ hydrogen doping during the magnetron sputtering process. As a result, the dark current of a-Ga₂O₃ UV PD is remarkably suppressed to 5.17 10^-11 A at a bias of 5 V. Importantly, the photocurrent of the corresponding device is still as high as 1.37 10^-3 A, leading to a high photo-to-dark current ratio of 2.65 10⁷ and the capability to detect the UV light with the intensity below 10 nW cm^-2. Moreover, the H-doped a-Ga₂O₃ thin films have also been deposited on polyethylene naphtholate substrates to construct flexible UV PDs, which exhibit no great degradation in bending states and fatigue tests. These results demonstrate that hydrogen doping can effectively improve the performance of a-Ga₂O₃ UV PDs, further promoting its practical application in various areas.