Bandgap Tunable ZnGaO Thin Films Grown by Atomic Layer Deposition for High-Performance Ultraviolet Photodetection
Yu‐Chang Chen, Guang Zeng, Si-Tong Ding, Cai-Yu Shi, Xuefeng Zhao, David Wei Zhang, Hong-Liang Lü
Abstract
Ga 2 O 3 -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 Ga 2 O 3 and ZnO layers, respectively. The as-investigated 15-nm ZGO films showed an accurate doping ratio and excellent uniformity. The bandgap ( E g ) 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 E g value. The Ga:Zn 5:5 PD presented high photo-to-dark current ratio of ∼7 × 10 4, high R of 17.6 A/W, and an excellent weak-light-detection ability shown by the linear dynamic range of ∼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.