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β-Ga2O3 epitaxial thin films were deposited using laser molecular beam epitaxy technique and oxygen atmosphere in situ annealed in order to reduce the oxygen vacancy. Metal/semiconductor/metal structured photodetectors were fabricated using as-grown film and annealed film separately. Au/Ti electrodes were Ohmic contact with the as-grown films and Schottky contact with the annealed films. In compare with the Ohmic-type photodetector, the Schottky-type photodetector takes on lower dark current, higher photoresponse, and shorter switching time, which benefit from Schottky barrier controlling electron transport and the quantity of photogenerated carriers trapped by oxygen vacancy significant decreasing.

A solar-blind photodetector based on β-GaO/NSTO (NSTO = Nb:SrTiO) heterojunctions were fabricated for the first time, and its photoelectric properties were investigated. The device presents a typical positive rectification in the dark, while under 254 nm UV light illumination, it shows a negative rectification, which might be caused by the generation of photoinduced electron-hole pairs in the β-GaO film layer. With zero bias, that is, zero power consumption, the photodetector shows a fast photoresponse time (decay time τ = 0.07 s) and the ratio I/I ≈ 20 under 254 nm light illumination with a light intensity of 45 μW/cm. Such behaviors are attributed to the separation of photogenerated electron-hole pairs driven by the built-in electric field in the depletion region of β-GaO and the NSTO interface, and the subsequent transport toward corresponding electrodes. The photocurrent increases linearly with increasing the light intensity and applied bias, while the response time decreases with the increase of the light intensity. Under -10 V bias and 45 μW/cm of 254 nm light illumination, the photodetector exhibits a responsivity R of 43.31 A/W and an external quantum efficiency of 2.1 × 10 %. The photo-to-electric conversion mechanism in the β-GaO/NSTO heterojunction photodetector is explained in detail by energy band diagrams. The results strongly suggest that a photodetector based on β-GaO thin-film heterojunction structure can be practically used to detect weak solar-blind signals because of its high photoconductive gain.

A self-powered ultraviolet photodetector with an extremely high responsivity (54.43 mA W−1) was fabricated by constructing p–n junction of GaN/Ga2O3 films.

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An epitaxial β-Ga2O3/Ga:ZnO heterojunction based self-powered DUV photodetector with an excellent wavelength selectivity and a high DUV/visible rejection ratio.

Solar-blind photodetectors have captured intense attention due to their high significance in ultraviolet astronomy and biological detection. However, most of the solar-blind photodetectors have not shown extraordinary advantages in weak light signal detection because the forewarning of low-dose deep-ultraviolet radiation is so important for the human immune system. In this study, a high-performance solar-blind photodetector is constructed based on the n-Ga2O3/p-CuSCN core–shell microwire heterojunction by a simple immersion method. In comparison with the single device of the Ga2O3 and CuSCN, the heterojunction photodetector demonstrates an enhanced photoelectric performance with an ultralow dark current of 1.03 pA, high photo-to-dark current ratio of 4.14 × 104, and high rejection ratio (R 254/R 365) of 1.15 × 104 under a bias of 5 V. Excitingly, the heterostructure photodetector shows high sensitivity to the weak signal (1.5 μW/cm2) of deep ultraviolet and high-resolution detection to the subtle change of signal intensity (1.0 μW/cm2). Under the illumination with 254 nm light at 5 V, the photodetector shows a large responsivity of 13.3 mA/W, superb detectivity of 9.43 × 1011 Jones, and fast response speed with a rise time of 62 ms and decay time of 35 ms. Additionally, the photodetector can work without an external power supply and has specific solar-blind spectrum selectivity as well as excellent stability even through 1 month of storage. Such prominent photodetection, profited by the novel geometric construction and the built-in electric field originating from the p–n heterojunction, meets greatly well the “5S” requirements of the photodetector for practical application.

Most of the photodetectors can measure all of the light illumination with a wavelength below the absorption edge of the detector materials, while they cannot distinguish the different waveband. Herein, a self-powered spectrum-distinguishable photoelectrochemical (PEC) type photodetector based on an α-Ga2O3 nanorod array (NA)/Cu2O microsphere (MS) p–n junction was reported. Under the combined action of the built-in electric field of the p–n junction and the semiconductor/electrolyte junction, the photodetector exhibits an opposite direction of the photocurrent to the illumination of 254 and 365 nm UV light under the applied bias of 0 V, which can be used to distinguish the different wavelengths of light. The photodetector shows a responsivity of 0.42 mA/W under 254 nm UV light and 0.57 mA/W upon 365 nm, respectively. Our results provide an idea for distinguishing the different illumination wavebands through a photodetector constructed by the heterojunction with two different band gap materials.