Yifan Jia

The β-Ga2O3 single-crystal nanobelts with defect-free surfaces have a clear geometric structure and nearly perfect crystallinity. This paper investigated the synthesis of large-sized β-Ga2O3 nanobelts and the related mechanisms. The as-synthesized β-Ga2O3 nanobelts with smooth surfaces have extremely high single-crystal quality. The surface crystal planes of nanobelts are (100), and the growth direction is [010] orientation. The growth process of the entire nanobelts can be divided into nucleation, expansion, equal-width, and shrink stages. Based on the synthesis mechanism, the largest β-Ga2O3 nanobelt to date, with a l width of 379 μm, has been prepared. This research should provide a potential technical way for the preparation of β-Ga2O3 single crystals.

(Al₂O₃)_x(HfO₂)_1−x films with varying compositions were deposited on silicon substrates via plasma-enhanced atomic layer deposition (PEALD), and metal-oxide-semiconductor (MOS) capacitors were fabricated. The impact of varying induced Al content on the dielectric properties of HfO₂ was examined through electrical measurements. The results showed that increasing Al content raised the flat-band voltage, reduced the interface state density (D_it), and significantly lowered the leakage current at a given voltage. Moreover, room temperature I-V measurements indicated that Schottky emission (~ 0.8–4.8 MV/cm), Poole-Frenkel (PF) emission (~ 4.8–7.3 MV/cm), and Fowler-Nordheim (FN) tunneling (~ 7.3–8.3 MV/cm) were the dominant current mechanisms under varying electric fields. At higher temperatures (75–100 °C), the leakage mechanism in Al-rich samples (50-100%) shifted from FN tunneling to PF emission at high electric fields (~ 3.3–6.87 MV/cm). The composition and energy band alignments of the films were characterized using X-ray photoelectron spectroscopy (XPS) and ultraviolet (UV) spectrophotometry, showing that introducing Al into HfO₂ increases the bandgap, reduces the dielectric constant, and significantly lowers oxygen vacancies. Thus, it is further demonstrated that HfO₂ films with the appropriate Al content can effectively enhance dielectric properties and adjust the material parameters of the dielectric layer.

A mild two-step method of black phosphorus (BP) flake thinning was demonstrated in this article. Slight ultraviolet–ozone (UVO) radiation followed by an argon plasma treatment was employed to oxidize mechanically exfoliated BP flakes and remove the surface remains of previous ozone treatment. The annealing process introduced aims to reduce impurities and defects. Low damage and efficient electronic devices were fabricated in terms of controlling the thickness of BP flakes through this method. These results lead to an important step toward the fabrication of high-performance devices based on two-dimensioned materials.

In this work, Ga2O3 thin films were deposited on c-plane sapphire substrates by atomic layer deposition technique followed by post annealing process. The influence of post annealing temperature on both their material characteristics and UV photoelectric properties were studied by ultraviolet-visible spectroscopy, X-ray diffraction, X-ray photo-electron spectroscopy and semiconductor parameter analyzer. When the post annealing temperature exceeds 700℃, the Ga2O3 films exhibits a nanocrystalline β-phase. The metal-semiconductor-metal solar-blind photodetectors based on Ga2O3 films annealed at different temperature were fabricated. The photo-current and responsivity first increase slowly and then decrease when the annealing temperature changes from 400℃ to 1000℃. An ultrahigh photoresponsivity of 142 A/W with detectivity of 3.77×1015 Jones under 254 nm illumination was achieved for the Ga2O3 film annealed at 600℃ for 90 min in N2/Air mixture atmosphere. However, the ultraviolet photoelectric responses of Ga2O3 films decrease sharply once the annealing temperature exceeds 800℃, which can be attributed to the Al diffuses into the Ga2O3 thin film from the sapphire substrate.

Hydrogen-nitrogen hybrid passivation treatment for growing high-property gate oxide films by high-temperature wet oxidation, with short-time NO POA, is proposed and demonstrated. Secondary ion mass spectroscopy (SIMS) measurements show that the proposed method causes hydrogen and appropriate nitrogen atoms to accumulate in Gaussian-like distributions near the SiO₂/SiC interface. Moreover, the hydrogen atoms are also incorporated into the grown SiO₂ layer, with a concentration of approximately 1 × 10¹⁹ cm⁻³. The conductance characteristics indicate that the induced hydrogen and nitrogen passivation atoms near the interface can effectively reduce the density of interface traps and near-interface traps. The current-voltage (I-V), X-ray photoelectron spectroscopy (XPS), and time-dependent bias stress (TDBS) with ultraviolet light (UVL) irradiation results demonstrate that the grown SiO₂ film with the incorporated hydrogen passivation atoms can effectively reduce the density of oxide electron traps, leading to the barrier height being improved and the leakage current being reduced.

In this paper the effects of 5 MeV proton irradiation on nitrided SiO₂/4H-SiC metal–oxide–semiconductor (MOS) capacitors are studied in detail and the related mechanisms are revealed. The density of interface states (Dit) is increased with the irradiation doses, and the annealing response suggests that the worse of Dit is mainly caused by displacement effect of proton irradiation. However, the X-rays photoelectron spectroscopy (XPS) measurement shows that the quantity proportion of breaking of Si≡N induced by displacement is only 8%, which means that the numbers of near interface electron traps (NIETs) and near interface hole traps (NIHTs) are not significantly changed by the displacement effect. The measurements of bidirectional high frequency (HF) C-V characteristics and positive bias stress stability show that the number of un-trapped NIETs and oxide electron traps decreased with increasing irradiation doses because they are filled by electrons resulted from the ionization effect of proton irradiation, benefiting to the field effective mobility (μ_FE) and threshold voltage stability of metal–oxide–semiconductor field-effect transistors (MOSFETs). The obviously negative shift of flat-band voltage (V_FB) resulted from the dominant NIHTs induced by nitrogen passivation capture more holes produced by ionization effect, which has been revealed by the experimental samples with different nitrogen content under same irradiation dose.