The ZnGa2O4 (ZGO) complex oxide with a wide bandgap of 5.1 eV has become one of the promising materials for deep ultraviolet sensing applications. However, the sputtered ZGO films always showed the disordered nanocrystalline structure resulting in the relatively poor performance. In this study, the solid-phase epitaxy method is used for crystallizing the ZGO structure via rapid thermal annealing (RTA) process. The disordered crystal-grains as incubated seeds are obtained in the as-deposited film at the substrate temperature of 400℃. By employing RTA at 700℃, the ZGO film structure approaches the quasi-single-crystalline structure, which is evidenced by checking the transmission electron microscopy. Suppression of the Zn diffusion out under the annealing will be discussed. As a result, the spectral responsivity of RTA-treated ZGO photodetector can reach 2.53 A W-1 at 240 nm and 5 V bias, indicating a relative enhancement of 256% as compared with the as-deposited one.
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