Gallium oxide thin films were deposited by radio frequency magnetron sputtering technique. Structural, optical and photoelectrical properties of Ga 2 O 3 thin films were investigated in detail. The as-grown Ga 2 O 3 thin films were amorphous, while those annealed film were polycrystalline with monoclinic structure. Amorphous and polycrystalline gallium oxide metal-semiconductor-metal photodetectors were fabricated. However, annealed polycrystalline films have no photoresponse for deep ultraviolet light. The responsivity of the photodetector based on as-grown amorphous film is 122.7 μA/W at 256 nm and the ultraviolet (UV)-to-visible rejection ratios were 100, which indicates that the amorphous Ga 2 O 3 thin films have potential application for solar-blind photodetector. High concentration of oxygen vacancies of amorphous film are considered to be responsible for photoresponse in amorphous gallium oxide thin films.

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The detection range of the Bi2O3 photodetector has been broadened to the NIR region through defect engineering.

In our work, (InxGa1-x)2O3 films were obtained on sapphire (0001) substrates by radio frequency magnetron sputtering. The influence of annealing temperature on crystalline structure, morphology, transmittance, and the optical band gap was investigated in detail. X-ray diffraction analysis showed that the as-prepared (InxGa1-x)2O3 film was amorphous and the crystal quality was improved with the increasing of annealing temperature. The (true4¯02) peak shifted to larger angle with the increasing of annealing temperature. Energy Dispersive Spectrometer analysis showed decreasing trend of In content. X-ray diffraction analysis and Energy Dispersive Spectrometer jointly indicated the peak shift due to the decreasing of In content and variation of tensile stress. The morphology feature of films was investigated by atomic force microscope. The island structure existed in the surface of films at the annealing temperature from 500°C to 900°C and when annealing temperature is 1000°C, islands disappeared and needle-like structure occurred. Transmittance spectra revealed excellence optical properties of films and absorption coefficient spectra showed the decreasing of band gaps of films with the increasing of annealing temperature. It could be attributed to the decreasing of In content and variation of tensile stress.

Bismuth telluride (Bi2Te3), as an emerging two-dimensional (2D) material, has attracted extensive attention from scientific researchers due to its excellent optoelectronic, thermoelectric properties and topological structure. However, the application research of Bi2Te3 mainly focuses on thermoelectric devices, while the research on optoelectronic devices is scarce. In this work, the morphology evolution and growth mechanism of 2D Bi2Te3 nanosheets with a thickness of 12 ± 3 nm were systematically studied by solvothermal method. Then, the Bi2Te3 nanosheets were annealed at 350 °C for 1 h and applied to self-powered photoelectrochemical-type broadband photodetectors. Compared with the as-synthesized Bi2Te3 photodetector, the photocurrent of the photodetector based on the annealed Bi2Te3 is significantly enhanced, especially enhanced by 18.3 times under near-infrared light illumination. Furthermore, the performance of annealed Bi2Te3 photodetector was systematically studied. The research results show that the photodetector not only has a broadband response from ultraviolet to near-infrared (365–850 nm) under zero bias voltage, but also obtains the highest responsivity of 6.6 mA W−1 under green light with an incident power of 10 mW cm−2. The corresponding rise time and decay time are 17 ms and 20 ms, respectively. These findings indicate that annealed Bi2Te3 nanosheets have great potential to be used as self-powered high-speed broadband photodetectors with high responsivity.

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