Effect of Annealing Temperature on the Properties of Gallium Oxide Thin Films and Ultraviolet Detectors

In this work, Gallium oxide (Ga2O3) thin films are deposited by radio frequency magnetron sputtering on quartz substrates at room temperature and control different annealing temperatures in argon atmosphere for the post-annealing process. The influence of annealing temperatures in the argon atmosphere on crystal structure, transmittance, surface morphology, and optical band gap of the samples are investigated in detail. It is found that the annealing process can improve the crystalline quality of the film, but high-temperature annealing can also easily cause oxygen elements in the film to escape from the film to form oxygen vacancies, and it is evidenced by XPS test results images. To obtain the effect of the annealing process on the performance of gallium oxide thin film detectors, the MSM photodetector based on the samples annealed at 800 °C, which is compared with untreated samples operated at a reverse bias voltage of 1.1V can achieve excellent comprehensive photo-detection properties for 254 nm ultraviolet light: The light-dark current ratio(I254/Idark), responsivity and specific detectivity are high as 1021.3, 0.106 A/W and 1.61×1012Jones, respectively, which are 7.5, 195 and 38.3 times that of the unannealed sample device. And the external quantum efficiency is improved by 51.6 %. The rise time of the 800 °C annealed sample detector (0.19/0.48 s) is reduced compared to the unannealed sample (0.93/0.93s), and the descent time of 800 ℃ detector（0.64/0.72 s） is increased compared to the unannealed sample（0.45/0.49 s）, respectively. By comparing the parameters with other current gallium oxide-based MSM photodetectors, It is found that the detector parameters of this work have some gaps compared with the current optimal parameters, which is attributed to the fact that the quartz substrate is selected for this work and not the sapphire substrate that is more matching with gallium oxide, resulting in the poor quality of the film compared with the sample on the sapphire substrate, and in this work, the photodetector have the high light-dark current ratio (PDCR) and detection rate (D*). In the end, the mechanism of increasing oxygen vacancies after annealing leading to improvement of detector performance parameters is analyzed in detail.