Fabrication of cerium-doped ß-Ga2O3 epitaxial thin films and deep ultraviolet photodetectors.

High-quality cerium-doped ß-Ga2O3 (Ga2O3:Ce) thin films could be achieved on (0001)α-Al2O3 substrates using a pulsed-laser deposition method. The impact of dopant contents concentration on crystal structure, optical absorption, photoluminescence, and photoelectric properties has been intensively studied. X-ray diffraction analysis results have shown that Ga2O3:Ce films are highly (2¯01) oriented, and the lattice spacing of the (4¯02) planes is sensitive to the Ce doping level. The prepared Ga2O3:Ce films show a sharp absorption edge at about 250 nm, meaning a high transparency to deep ultraviolet (DUV) light. The photoluminescence results revealed that the emissions were in the violet-blue-green region, which are associated with the donor-acceptor transitions with the Ce3+ and oxygen vacancies related defects. A simple DUV photodetector device with a metal-semiconductor-metal structure has also been fabricated based on Ga2O3:Ce thin film. A distinct DUV photoresponse was obtained, suggesting a potential application in DUV photodetector devices.

Broadband Ultraviolet Self-Powered Photodetector Constructed on Exfoliated ß-Ga2O3/CuI Core-Shell Microwire Heterojunction with Superior Reliability.

A heterojunction is an essential strategy for multispectral energy-conservation photodetection for its ability to separate photogenerated electron-hole pairs and tune the absorption edge by selecting semiconductors with appropriate bandgaps. A broadband ultraviolet (200-410 nm) self-powered photodetector is constructed on the exfoliated ß-Ga2O3/CuI core-shell microwire heterostructure. Benefiting from the photovoltaic and photoconductive effects, our device performs an excellent ultraviolet (UV) discriminability with a UVC/visible rejection ratio (R225/R600) of 8.8 × 103 and a UVA/visible rejection ratio (R400/R600) of 2.7 × 102, and a self-powered photodetection with a responsivity of 8.46 mA/W, a detectivity of 7.75 × 1011 Jones, an on/off switching ratio of 4.0 × 103, and a raise/decay speed of 97.8/28.9 ms under UVC light. Even without encapsulation, the photodetector keeps a superior stability over ten months. The intrinsically physical insights of the device behaviors are investigated via energy band diagrams, and the charge carrier transfer characteristics of the ß-Ga2O3/CuI interface are predicted by first principle calculation.

ß-Ga2O3 nanorod arrays with high light-to-electron conversion for solar-blind deep ultraviolet photodetection.

Vertically aligned nanorod arrays (NRAs), with effective optical coupling with the incident light and rapid electron transport for photogenerated carriers, have attracted much interest for photoelectric devices. Herein, the monoclinic ß-Ga2O3 NRAs with an average diameter/length of 500 nm/1.287 µm were prepared by the hydrothermal and post-annealing method. Then a circular Ti/Au electrode was patterned on ß-Ga2O3 NRAs to fabricate solar-blind deep ultraviolet photodetectors. At zero bias, the device shows a photoresponsivity (R λ) of 10.80 mA W-1 and a photo response time of 0.38 s under 254 nm light irradiation with a light intensity of 1.2 mW cm-2, exhibiting a self-powered characteristic. This study presents a promising candidate for use in solar-blind deep ultraviolet photodetection with zero power consumption.