The Effect of Annealing Ambience on the Material and Photodetector Characteristics of Sputtered ZnGa2O4 Films

Spinel ZnGa2O4 films were grown on c-plane sapphire substrates at the substrate temperature of 400 degrees C by radio-frequency magnetron sputtering. Post thermal annealing was employed at the annealing temperature of 700 degrees C in order to enhance their crystal quality. The effect of thermal annealing on the microstructural and optoelectronic properties of ZnGa2O4 films was systematically investigated in various ambiences, such as air, nitrogen, and oxygen. The X-ray diffraction patterns of annealed ZnGa2O4 films showed the crystalline structure to have (111) crystallographic planes. Transmission electron micrographs verified that ZnGa2O4 film annealed under air ambience possesses a quasi-single-crystalline structure. This ZnGa2O4 film annealed under air ambience exhibited a smooth surface, an excellent average transmittance above 82% in the visible region, and a wide bandgap of 5.05 eV. The oxygen vacancies under different annealing ambiences were revealed a substantial impact on the material and photodetector characteristics by X-ray photoelectron spectrum investigations. ZnGa2O4 film exhibits optimal performance as a metal-semiconductor-metal photodetector when annealed under air ambience. Under these conditions, ZnGa2O4 film exhibits a higher photo/dark current ratio of similar to 10(4) order, as well as a high responsivity of 2.53 A/W at the bias of 5 V under an incident optical light of 240 nm. These results demonstrate that quasi-single-crystalline ZnGa2O4 films have significant potential in deep-ultraviolet applications.

Automated summary

The study investigated the effect of thermal annealing in different ambients on the microstructural and optoelectronic properties of ZnGa2O4 films, finding that ZnGa2O4 films annealed under air ambiance exhibited excellent optoelectronic performance and quasi-single-crystalline structure, suitable for metal-semiconductor-metal photodetectors.