Substrate temperature dependent crystal structure and deep-ultraviolet photodetection of ZnGa2O4 thin films ∗

Zinc gallate (ZnGa 2 O 4 ) is a promising material for deep-ultraviolet (DUV) photodetectors, owing to its wide bandgap and high transparency. However, the effect of substrate temperature on the structural and optical properties of ZnGa 2 O 4 thin films prepared by magnetron sputtering is not well understood. Here, we report a systematic study of the influence of substrate temperature on the crystal quality, stoichiometry, bandgap, and photodetection performance of ZnGa 2 O 4 thin films deposited on sapphire substrates. We find that the films undergo a phase transition from amorphous to polycrystalline at 300 °C, and then to single crystalline at 500 °C, accompanied by an increase in the bandgap from 4.6 to 4.9 eV. We also fabricate metal-semiconductor–metal photodetectors based on the ZnGa 2 O 4 thin films with Ti/Au electrodes, which exhibit excellent Ohmic contact and high light-to-dark current ratio. The photodetectors show remarkable and stable DUV response, with the highest performance achieved at a substrate temperature of 650 °C. Our results demonstrate the crucial role of substrate temperature in tailoring the crystal structure and DUV photodetection of ZnGa 2 O 4 thin films, and provide a facile route for optimizing their performance.