Self-powered ${\mathrm{Ga}}_2{\mathrm{O}}_3$-based solar-blind photodetectors have received attention recently due to the increased demand for energy saving, miniaturization, and high efficiency in devices. An ideal device structure consisting of a ${\mathrm{Ga}}_2{\mathrm{O}}_3$-based p-n junction is still difficult to obtain, since p-type doping is a major challenge. Although self-powered devices based on heterojunction are promising, there are two fatal disadvantages: (1) photosensitivity of the non-solar-blind region, on account of the narrower band gap of the heterojunction materials; and (2) poor quality of the epitaxial film due to lattice mismatch. In view of the various polymorphs of ${\mathrm{Ga}}_2{\mathrm{O}}_3$, we propose constructing a structure consisting of a ${\mathrm{Ga}}_2{\mathrm{O}}_3$ phase junction with α and β phases (α/β phase junction) for self-powered solar-blind photodetectors. The small lattice mismatch and similar band gap between α- and β-${\mathrm{Ga}}_2{\mathrm{O}}_3$ will solve the two problems outlined above. The formation of α- and β-${\mathrm{Ga}}_2{\mathrm{O}}_3$ is expected to result in a type-II band alignment, promoting separation of photogenerated carriers, which transfer through the junction to the corresponding electrodes. Herein, the α/β phase junction of ${\mathrm{Ga}}_2{\mathrm{O}}_3$ vertically aligned nanorod arrays with a thickness-controllable β-${\mathrm{Ga}}_2{\mathrm{O}}_3$ shell layer are fabricated by a low-cost and simple process of hydrothermal and postannealing treatment. Two different types of self-powered α/β-${\mathrm{Ga}}_2{\mathrm{O}}_3$ phase junction-based photodetectors, in the form of solid-state type and photoelectrochemical type, are constructed and realized. Our analysis shows that the constructed photodetectors are capable of highly efficient detection of solar-blind signal without any bias voltage. This work demonstrates the usefulness of using the α/β-${\mathrm{Ga}}_2{\mathrm{O}}_3$ phase junction in a self-powered solar-blind photodetector, which is not only energy efficient, but also potentially workable in outer space, at the south and north pole, and other harsh environments without external power for a long time.

• Received 28 August 2019
• Revised 27 December 2019
• Accepted 4 February 2020

DOI:https://doi.org/10.1103/PhysRevApplied.13.024051