Quasi‐Single‐Crystalline ZnGa 2 O 4 Films via Solid Phase Epitaxy for Enhancing Deep‐Ultraviolet Photoresponse

The complex‐oxide materials are multifunctional materials, which have wide applications to the semiconductor and microelectronic fields. The ZnGa 2 O 4 having a wide bandgap of 5.1 eV is one of the promising materials for deep‐ultraviolet photodetector (PD) applications. The ZnGa 2 O 4 films are deposited by using conventional radio‐frequency magnetron sputtering which is extensively employed in the industry. However, the as‐deposited ZnGa 2 O 4 films show the disordered nanocrystalline structure, resulting in the relatively poor performance. Since the Zn atoms can diffuse out of the film structure during the annealing, the ZnGa 2 O 4 material is difficult to get the single‐crystalline structure by using the sputtering method. Here, the solid‐phase epitaxy method is used for crystallizing the ZnGa 2 O 4 structure via rapid thermal annealing process. The disordered crystal grains as incubated seeds are obtained in the as‐deposited ZnGa 2 O 4 film at the substrate temperature of 400 °C. Further annealing under the temperature of 700 °C in 1 min, the ZnGa 2 O 4 film structure approaches the quasi‐single‐crystalline ZnGa 2 O 4 structure, which is evidenced by checking the transmission electron microscopy. The responsivity of annealed ZnGa 2 O 4 PDs can reach 2.53 A W −1 (at 240 nm and 5 V), which shows a relative enhancement of 256% compared with the as‐deposited ZnGa 2 O 4 PDs.