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Gallium oxide (Ga2O3) is attracting attention as a next-generation semiconductor material for power device because it has a wide energy band gap and high breakdown electric field. We deposited a Sn polymer, poly-tetraallyl tin, on Ga2O3 samples using a disclosed initiated chemical vapor deposition (iCVD) process. The Sn dopant of the Sn polymer layer is injected into the Ga2O3 through a heat treatment process. Diffusion model of Sn into the Ga2O3 is proposed through secondary ion mass spectroscopy analysis and bond dissociation energy. The fabricated device exhibited typical n-type field-effect transistor (FET) behavior. Ga2O3 Sn-doping technology using iCVD will be applied to 3D structures and trench structures in the future, opening up many possibilities in the Ga2O3-based power semiconductor device manufacturing process. [ABSTRACT FROM AUTHOR]

The electrical and optoelectronic performance of semiconductor devices are mainly affected by the presence of defects or crystal imperfections in the semiconductor. Oxygen vacancies are one of the most common defects and are known to serve as electron trap sites whose energy levels are below the conduction band (CB) edge for metal oxide semiconductors, including β-Ga2O3. In this study, the effects of plasma nitridation (PN) on polycrystalline β-Ga2O3 thin films are discussed. In detail, the electrical and optical properties of polycrystalline β-Ga2O3 thin films are compared at different PN treatment times. The results show that PN treatment on polycrystalline β-Ga2O3 thin films effectively diminish the electron trap sites. This PN treatment technology could improve the device performance of both electronics and optoelectronics. [ABSTRACT FROM AUTHOR]

The photocatalytic degradation of formaldehyde, acetaldehyde, toluene, and styrene are compared using monoclinic Ga2O3 and anatase TiO2 nanostructures under ultraviolet-C irradiation. These Ga2O3 and TiO2 photocatalysts are characterized using a field emission scanning electron microscope, a powder X-ray diffraction system, the Brunauer–Emmett–Teller method, and a Fourier transform infrared spectrometer. The Ga2O3 shows a higher reaction rate constant (k, min−1) than TiO2 by a factor of 7.1 for toluene, 8.1 for styrene, 3.1 for formaldehyde, and 2.0 for acetaldehyde. The results demonstrate that the photocatalytic activity ratio of the Ga2O3 over the TiO2 becomes more prominent toward the aromatic compounds compared with the nonaromatic compounds. Highly energetic photo-generated carriers on the conduction/valence band-edge of the Ga2O3, in comparison with that of the TiO2, result in superior photocatalytic activity, in particular on aromatic volatile organic compounds (VOCs) with a high bond dissociation energy. [ABSTRACT FROM AUTHOR]

β-Ga2O3 has attracted considerable attention as an alternative photocatalyst to replace conventional TiO2 under ultraviolet-C irradiation due to its high reduction and oxidation potential. In this study, to enhance the photocatalytic activity of β-Ga2O3, nanofibers are formed via the electrospinning method, and Si atoms are subsequently doped. As the Si concentration in the β-Ga2O3 nanofiber increases, the optical bandgap of the β-Ga2O3 nanofibers continuously decreases from 4.5 eV (intrinsic) to 4.0 eV for the Si-doped (2.4 at. %) β-Ga2O3 nanofibers, and accordingly, the photocatalytic activity of the β-Ga2O3 nanofibers is enhanced. This higher photocatalytic performance with Si doping is attributed to the increased doping-induced carriers in the conduction band edges. This differs from the traditional mechanism in which the doping-induced defect sites in the bandgap enhance separation and inhibit the recombination of photon-generated carriers. [ABSTRACT FROM AUTHOR]

[Display omitted] • A transistor-type photodetector (PD) can control the channel current. • Normally-off transistor-type PDs have advantages such as low leakage current. • Ga 2 O 3 N-doping enhances insulation and enables precise control of channel thickness. • It exhibits stable and fast switching characteristics under pulsed bias voltage. • The shortest rise and decay times of 3.8 ms and 3.5 ms, respectively, achieved. β -phase gallium oxide (β-Ga 2 O 3) is attracting attention as a deep—ultraviolet photodetector (PD) owing to its large band gap of 4.9 eV, almost direct band gap characteristics, and solar-blind photodetection. However, most Ga 2 O 3 -based transistor-type PDs operate in a normally-on mode. In this study, a silicon (Si)-doped β -Ga 2 O 3 epilayer with normally-off characteristics was grown on a nitrogen (N)-doped buffer layer of a c -plane Al 2 O 3 substrate using metal–organic chemical vapor deposition. The N-doped layer acts as a buffer layer during Si-doped β -Ga 2 O 3 growth and improves crystallinity. In addition, the N-doped buffer layer has semi-insulating properties that reduce leakage current, enabling precise control of the effective thickness of the Si-doped β -Ga 2 O 3 epilayer. Phototransistors are fabricated to improve the characteristics of ultraviolet PDs, such as photo-to-dark current ratio and on–off time. The Si-doped β -Ga 2 O 3 -based transistor-type PD has a detectivity of 3.85 × 1016 Jones at a wavelength of 260 nm. It achieves detectivity values similar to those of flake-based PDs, and performs the best amongst non-flake-based PDs. Moreover, its rising time and decay time are 3.8 ms and 3.5 ms, respectively; these are among the smallest values reported for existing Ga 2 O 3 -based transistor-type PDs. The fabricated epilayer will facilitate the fabrication of high-performance and efficient photo-electronic devices. [ABSTRACT FROM AUTHOR]

Al and In dopants are codoped in β -Ga 2 O 3 nanostructures via hydrothermal synthesis. Unlike single-dopant β -Ga 2 O 3 nanostructures, less mechanical strain is induced in the β -Ga 2 O 3 nanostructures with the codoping of Al and In atoms. This is attributed to the size compensation effect. The induced mechanical strain caused by each dopant in the β -Ga 2 O 3 nanostructures is analyzed using X-ray diffraction. Chemical states are also compared after Al and In doping in the β -Ga 2 O 3 nanostructures. Finally, the photocatalytic properties of various β -Ga 2 O 3 nanostructures at different Al and In concentrations are compared via the decomposition of methylene blue from UVC irradiation with a wavelength of 254 nm. Compared to the single-dopant β -Ga 2 O 3 nanostructures, enhanced photocatalytic activity is obtained with higher dopant concentrations when Al and In atoms are codoped in the β -Ga 2 O 3 nanostructures. This codoping technique could be applied to various applications where higher doping concentrations are advantageous while minimizing the induced lattice deformation of the β -Ga 2 O 3. [Display omitted] • Al dopants induce compressive strain in β -Ga 2 O 3 nanostructures. • In dopants induce tensile strain in β -Ga 2 O 3 nanostructures. • Nearly strain-free structure forms via codoping of Al and In atoms. • Enhanced photocatalytic activity is obtained with codoping of Al and In atoms. [ABSTRACT FROM AUTHOR]

The reversible photoinduced wettability of β-Ga 2 O 3 thin films with different film thicknesses is investigated under ultraviolet C irradiation, and the results are compared with those from an amorphous SiO 2 surface. The Ga 2 O 3 surface exhibits reversible photoinduced wettability under ultraviolet-C (UVC) radiation centered at 254 nm. The critical transition time (CTT) of the 50-nm thick β-Ga 2 O 3 film is comparable to that of the 8-nm thick β -Ga 2 O 3 film, but the CTT value increases significantly for the 100-nm thick β -Ga 2 O 3 film. The thickness-dependent reversible wettability in the Ga 2 O 3 surface is explained using a penetration-diffusion model. The photoinduced Ga 2 O 3 surface also exhibits substantial antimicrobial activity in Escherichia coli cells. The experimental findings in this work indicate that Ga 2 O 3 can be used in various applications, including self-cleaning, anti-fogging, and antimicrobial activities. • The surface of Ga 2 O 3 is activated under ultraviolet-C irradiation. • The rate of photoinduced wettability changes depending on Ga 2 O 3 thickness. • The photoinduced Ga 2 O 3 surface exhibits antibacterial activity. [ABSTRACT FROM AUTHOR]