Enhanced photo-response performance of Cu2O-based graded heterojunction optoelectronic devices with a Ga2O3 buffer layer

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2022-04, Vol.10 (14), p.5505-5513
• Main Authors: Meng, Xiao, Dong, Kailian, Liang, Jiwei, He, Jin, Guojia Fang
• Format: Article
• Language: English
• Subjects: Absorptivity; Buffer layers; Carrier recombination; Charge transport; Conduction bands; Copper oxides; Current carriers; Devices; Energy bands; Energy gap; Energy levels; Gallium oxides; Heterojunctions; Hole mobility; Optoelectronic devices; Oxygen; Photometers; Pulsed laser deposition; Pulsed lasers; Quantum efficiency; Stability; Toxicity; Ultraviolet detectors; Zinc oxide
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/d2tc00652a

Cuprous oxide (Cu2O) has been widely investigated in optoelectronic devices because of its non-toxicity, high optical absorption coefficient, intrinsic p-type conductivity, and high hole mobility. However, misaligned energy levels remain an obstacle to obtaining efficient optoelectronic devices due to the extremely high conduction band minimum of Cu2O. Here, a band-aligned wide bandgap Ga2O3 buffer layer is introduced and a graded heterojunction ZnO/Ga2O3/Cu2O is realized. The oxygen-vacancy concentration and therefore the Fermi level, optical transmittance, and bandgap of the Ga2O3 films can be tuned by controlling the oxygen environment during pulsed laser deposition. The performance of the optoelectronic devices is improved by incorporating an optimized Ga2O3 buffer layer deposited at 1 Pa oxygen pressure with a deposition temperature of 100 °C. Photodetectors with a response range from the near-ultraviolet to the visible-light region, good linearity, fast response, and excellent long-term stability are demonstrated. In the meantime, an enhancement of the external quantum efficiency of 66% was reached by inserting the Ga2O3 buffer layer. Heterojunctions with gradient energy bands are confirmed to be effective in accelerating charge transport and suppressing carrier recombination through Kelvin probe force microscopy (KPFM) studies. Our work provides a new approach for developing self-powered ultraviolet and visible-light photodetectors with low-cost and high stability.