Under-Seawater Immersion ß-Ga2O3 Solar-Blind Ultraviolet Imaging Photodetector with High Photo-to-Dark Current Ratio and Fast Response.

This work displays a photovoltaic solar-blind UV photodetector based on a ß-Ga2O3 photoelectrode/simulated seawater (NaCl). The photodetector exhibits extremely high photocurrent (6.70 µA); the responsivity can reach 23.47 mA W-1, and the fastest response rise time is 40 ms under 213 nm illumination at zero bias, the responsivity is 25.10 mA W-1 at 0.8 V, and the photo-to-dark current ratio reaches a maximum of 4663, whose responsivity can be effectively adjusted by changing electrolyte concentration, ensuring a good working stability of this device. In addition, with original seawater as the electrolyte, the detector still achieves a high switching ratio (754) and stable detection under zero bias, demonstrating its capability for practical uses. What's more, we present the capability of the photodetector in seawater imaging. This work provides a method for solar-blind UV detection in seawater, which compensates for the limited detection of most current seawater detectors in the visible band, and can provide certain guidance in the field of seawater detection.

Ultra-Hard (41 GPa) Isotopic Pure 10BP Semiconductor Microwires for Flexible Photodetection and Pressure Sensing.

An urgent demand for electronic and optoelectronic devices able to work in extreme environments promotes a series of research studies on semiconductor materials. Cubic boron phosphide (BP) as a semiconductor material with excellent characteristics shows great application potential. However, since the synthesis conditions required are difficult to achieve and the growth mechanism of BP is still unclear, there are few reports on the basic properties of BP and pure isotope BP, resulting in a narrow understanding of their special physical properties. Here, we successfully obtained highly pure isotopic 10BP crystals by a vapor-liquid-solid (VLS) method unconventionally designed, which successfully overcomes the thermodynamic conflict between the high melting point of the boron element and low sublimation temperature of the phosphorus element. The 10BP achieved owns an aspect ratio as high as 104 and a hardness up to 41 GPa. Besides, as an indirect bandgap semiconductor, it has ultrawide red emission spectra, a p-type conductivity with extremely low resistivity, and excellent photoelectronic and piezoelectric characteristics. Furthermore, compared with other superhard semiconductors like cubic BN and diamond, 10BP has an obvious advantage of lower growth temperature (1200 °C). All these characteristics confirm the prospects owned by 10BP in its applications to the field of high-conductivity, optoelectronic, strain-sensing, and superhard semiconductors.

Pt/ZnGa2O4/p-Si Back-to-Back Heterojunction for Deep UV Sensitive Photovoltaic Photodetection with Ultralow Dark Current and High Spectral Selectivity.

In this work, a strategy of constructing a back-to-back heterojunction is proposed to fabricate Si-based photovoltaic photodetectors with high deep ultraviolet (DUV) spectral selectivity. By combining Pt with a thickness of 4 nm with a ZnGa2O4/Si heterojunction, a back-to-back heterojunction is successfully constructed. Based on that, a Pt/ZnGa2O4/p-Si DUV photovoltaic detector with a low dark current density (∼9.6 × 10-5 µA/cm2), a large photo-to-dark current ratio (PDCR, >105), and a fast response speed (decay time <50 ms) is fabricated. At 0 V bias, this device displays a photoresponsivity of about 1.36 mA/W and a high deep ultraviolet-visible (DUV-vis) rejection ratio (R258 nm/R420 nm) of ∼1.1 × 105, which are 1-2 orders of magnitude higher than those of most photovoltaic DUV detectors reported currently. Even at a working temperature of 470 K, the detectivity of this device can still reach ∼1.23 × 1010 Jones. In addition, compared with Au/ZnGa2O4/Si devices, the dark current and PDCR of this Pt/ZnGa2O4/Si device decrease by 2 orders of magnitude and increase by 1 order of magnitude, respectively. The enhanced performance of this ZnGa2O4/Si device can be attributed to the higher Schottky barrier established between Pt with a higher work function and ZnGa2O4. This strategy of adopting a back-to-back heterojunction device structure to hinder the visible light photoresponse of Si-based photodetectors and thus to reduce the dark current of a device can provide a reference for preparing photovoltaic DUV detectors with excellent performance.