α-Ga2O3, with an ultra-high energy bandgap of 5.1 eV, is an attractive material for applications in solar-blind photodetectors and high-power electronics. We fabricated an α-Ga2O3 metal-semiconductor-metal (MSM) interdigitated solar-blind photodetector, where an epitaxial α-Ga2O3 thin film was grown on a sapphire substrate using a hydride vapor-phase epitaxy technique. Excellent optoelectronic device properties including high responsivity (4.24 × 104 A/W), detectivity (1.77 × 1011 Jones), and external quantum efficiency (2.07 × 105) were demonstrated in response to ultraviolet (UV) C wavelength. Under sunlight, the α-Ga2O3 MSM photodetector exhibited stable solar-blind sensitivity to UVC wavelength without interference from the incoming solar spectrum. Our work proposes that α-Ga2O3 has great potential as a next-generation high-performance solar-blind photodetector.

Among various polymorphic phases of gallium oxide (Ga₂O₃), α-phase Ga₂O₃ has clear advantages such as its heteroepitaxial growth as well as wide bandgap, which is promising for use in power devices. In this work, we demonstrate α-Ga₂O₃ MOSFETs with hybrid Schottky drain (HSD) contact, comprising both Ohmic and Schottky electrode regions. In comparison with conventional Ohmic drain (OD) contact, a lower on-resistance (R_on) of 2.1 kΩ mm is achieved for variable channel lengths. Physics-based TCAD simulation is performed to validate the turn-on characteristics of the Schottky electrode region and the improved R_on. Electric-field analysis in the off-state is conducted for both the OD and HSD devices. Furthermore, a record breakdown voltage (BV) of 2.8 kV is achieved, which is superior to the 1.7 kV of the compared OD device. Our results show that the proposed HSD contact with a further optimized design can be a promising drain electrode scheme for α-Ga₂O₃ power MOSFETs.

The compound α-Ga₂O₃ is an ultra-wide-bandgap semiconductor and possesses outstanding properties such as a high breakdown voltage and symmetry compared with other phases. It has been studied for applications in high-performance power devices. However, it is difficult to obtain a high-quality thin films because α-Ga₂O₃ can only grow heteroepitaxially, which results in residual stress generation owing to lattice mismatch and thermal expansion between the substrate and α-Ga₂O₃. To overcome this, α-Ga₂O₃ was grown on a conical frustum-patterned sapphire substrate by halide vapor-phase epitaxy. The surface morphology was crack-free and flat. The α-Ga₂O₃ grown on a frustum-patterned substrate and a conventional sapphire substrate at 500°C exhibited full-width at half-maxima of 961 and 1539 arcsec, respectively, for 10–12 diffraction. For the former substrate, lateral growth on the pattern and threading dislocation bending towards the pattern suppressed the propagation of threading dislocations generated at the interface, which reduced the threading dislocation propagation to the surface by half compared with that on the latter conventional substrate. The results suggest that conical frustum-patterned sapphire substrates have the potential to produce high-quality α-Ga₂O₃ epilayers.

In this work, we have achieved synthesizing large-area high-density β-Ga₂O₃ nanowires on c-plane sapphire substrate by metal–organic chemical vapor deposition assisted with Au nanocrystal seeds as catalysts. These nanowires exhibit one-dimensional structures with Au nanoparticles on the top of the nanowires with lengths exceeding 6 μm and diameters ranging from ~50 to ~200 nm. The β-Ga₂O₃ nanowires consist of a single-crystal monoclinic structure, which exhibits strong ( $\overline{2}$ 01) orientation, confirmed by transmission electronic microscopy and X-ray diffraction analysis. The PL spectrum obtained from these β-Ga₂O₃ nanowires exhibits strong emissions centered at ~360 and ~410 nm, respectively. The energy band gap of the β-Ga₂O₃ nanowires is estimated to be ~4.7 eV based on an optical transmission test. A possible mechanism for the growth of β-Ga₂O₃ nanowires is also presented.