Bandgap Tunable ZnGaO Thin Films Grown by Atomic Layer Deposition for High-Performance Ultraviolet Photodetection

Ga2O3-doped thin films exhibit great potential in terms of optical and electronic properties. However, efforts are needed to meet the challenge of obtaining high-quality films by doping to achieve high-performance ultraviolet (UV) detection with tunable detection wavelengths. In this work, zinc-doped gallium oxide (ZGO) thin films with different Ga:Zn ratios were prepared by atomic layer deposition (ALD). During the film deposition, the plasma-enhanced ALD and thermal ALD were used alternately to grow Ga2O3 and ZnO layers, respectively. The as-investigated 15-nm ZGO films showed an accurate doping ratio and excellent uniformity. The bandgap (Eg) was found to be well-tunable from 4.45 eV to 3.21 eV with increasing Zn content. The electronic band structures and the relationship between energy levels were analyzed in detail. Furthermore, metal-semiconductor-metal devices based on the Ga:Zn 9:1, 5:5, and 1:9 films were fabricated for UV detection. The ZGO thin film photodetectors (PDs) exhibited extremely low dark current and an obvious rejection ratio of the responsivity (R) of 254 and 365 nm light, showing the trend in accordance with the Eg value. The Ga:Zn 5:5 PD presented high photo-to-dark current ratio of similar to 7 x 10(4), high R of 17.6 A/ W, and an excellent weak-light-detection ability shown by the linear dynamic range of similar to 96.8 dB under 254 nm illumination. This work can fill the void of the doping research field and provide a feasible scheme for the development of a high-sensitivity photoelectric system.