Abstract:  Due to its low background noise, solar-blind ultraviolet photodetection technology is widely used in fields such as fire monitoring, missile detection, and military communication. Compared to other solar-blind ultraviolet sensitive materials, amorphous gallium oxide offers several advantages, including a bandgap that matches the solar-blind ultraviolet region, structural stability, and good mechanical strength. The horizontal metal-semiconductor-metal structured photodetectors are known for their simple production processes, ease of integration, and suitability for industrialization. Given the non-uniform distribution of the internal electric field and the photo-generated carriers along the thickness direction in horizontal devices, the thickness of the photoreceptive layer plays a crucial role in the performance of the photodetectors. In order to fabricate high- performance solar-blind ultraviolet photodetectors, amorphous gallium oxide thin films were prepared using low- temperature metal organic chemical vapor deposition method. Structural characterization of the films confirmed their amorphous nature, and the film surfaces were found to be relatively flat, with the optical absorption edge located within the deep ultraviolet spectral range. Solar-blind ultraviolet photodetectors were subsequently developed. As the thickness of the photoreceptive layer increased from 33. 2 nm to 133. 6 nm, the dark-current of the photodetector rose from 2. 33*10^-10 A to 2. 12*10^-8 A, and the photo-current under 254 nm illumination increased from 1. 66 * 10^-7 A to 3. 2 * 10^-5 A. Additionally, both the responsivity and the external quantum efficiency of the photodetectors increased by orders of magnitude with the increase in the photoreceptive layer thickness, reaching maximum values of 2. 91 A/ W and 1 419. 12% , respectively. The thickness-dependent characteristics of the photodetectors can be attributed to the interfacial high-defect layers, light absorption intensity, and the geometric parameters of the photodetectors. The photodetectors exhibited excellent wavelength selectivity, the current of each photo-detector under 365 nm illumination and the photo-current under 254 nm illumination differ by more than two orders of magnitude. Moreover, over the tested 5 cycles, the response / recovery behavior of each photodetector consistently demonstrates good repeatability and stability.

Key words: amorphous gallium oxide, solar-blind ultraviolet detection, thickness-dependent properties, metal organic chemical vapor deposition