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Ultrawide bandgap aluminum nitride (AlN) stands out as a highly attractive material for high-power electronics. However, AlN power devices face performance challenges due to high contact resistivity exceeding 10−1 Ω cm2. In this Letter, we demonstrate achieving a low contact resistivity at the 10−4 Ω cm2 level via refined metallization processes applied directly to n-AlN. The minimum contact resistivity reached 5.82 × 10−4 Ω cm2. Our analysis reveals that the low contact resistance primarily results from the stable TiAlTi/AlN interface, resilient even under rigorous annealing conditions, which beneficially forms a thin Al–Ti–N interlayer, promotes substantial nitrogen vacancies, enhances the net carrier density at the interface, and lowers the contact barrier. This work marks a significant milestone in realizing superior Ohmic contacts for n-type AlN, paving the way for more efficient power electronic and optoelectronic devices. [ABSTRACT FROM AUTHOR]

Traditional chemical solution deposition (CSD) methods for growing Ga2O3 films face two main issues: limited thickness per deposition, necessitating multiple coating-annealing cycles for adequate film thickness, and a decline in crystal quality with increased thickness. This study introduces an innovative CSD technique for fabricating (GaAl)2O3 films, achieving both high thickness and superior crystal quality, where the aluminum content results from the diffusion of aluminum from sapphire substrates during annealing. The technique uses a precursor solution with high viscosity and cation concentration, allowing single-layer thicknesses of up to 180 nm. Additionally, the incorporation of silver nitrate for silver doping enhances nucleation, growth, and epitaxial quality, inducing a unique twelve-fold symmetry in the (−201) oriented (GaAl)2O3 films. Notably, silver serves as a catalyst and largely evaporates at high temperatures, thus preserving the film's final composition and performance. This study highlights the effectiveness of this CSD approach in simultaneously improving crystal quality and achieving desired film thickness, making it a promising method for mass production of high-quality (GaAl)2O3 films. [ABSTRACT FROM AUTHOR]

In this research, β-Ga2O3/NiO heterostructures were grown directly on CeO2 buffered Hastelloy flexible substrates. With pulsed laser deposition under high temperatures, as-grown β-Ga2O3 and NiO thin films have a preferred out-of-plane orientation along the ⟨−201⟩ and ➎111➉ directions. This is due to the ideal epitaxial ability of the CeO2 buffer layer, which serves as a perfect template for the epitaxial growth of single-oriented NiO and β-Ga2O3 by creating a constant gradient from CeO2 (2.7 Å along ➎001➉) to NiO (2.9 Å along ➎110➉), and eventually to β-Ga2O3 (3.04 Å along ➎010➉). The Hastelloy substrates endow photodetectors with good deformability and mechanical robustness. Moreover, owing to the type-II band alignment of β-Ga2O3/NiO heterostructures, the photodetectors have a good photocurrent at zero bias under 284 nm of light illumination. In addition, the photocurrent is significantly higher than when using an analogous heterostructure (as described in some previous reports), because the β-Ga2O3 and NiO thin films are crystalized along a single orientation with fewer defects. [ABSTRACT FROM AUTHOR]

The reactive ion etching (RIE) process is needed to fabricate deep ultraviolet (DUV) light-emitting diodes (LEDs). However, the n-contact performance deteriorates when the high-Al n-AlGaN surface undergoes RIE, leading to decreased LED performance. In this study, we employed an atomic layer etching (ALE) technology to eliminate surface damage generated during the mesa etching process, thus enhancing the n-Al 0.65 Ga 0.35 N ohmic contact. The improved contact performance reduced LED operation voltage and mitigated device heat generation. It was observed that DUV LEDs treated with 200 cycles of ALE showed a reduction in operating voltage from 8.3 to 5.2 V at 10 mA, with a knee voltage of 4.95 V. The peak wall plug efficiency (WPE) was approximately 1.74 times that of reference devices. The x-ray photoelectron spectroscopy (XPS) analysis revealed that ALE removed the surface damage layer induced by plasma etching, eliminating surface nitrogen vacancies and increasing surface electron concentration. Consequently, it facilitated better ohmic contact formation on n-Al 0.65 Ga 0.35 N. This study demonstrates that the ALE technology achieves etching with minor surface damage and is suitable for use in III-nitride materials and devices to remove surface defects and contaminations, leading to improved device performance.

This work studies the impact of the silicon (Si) loading effect induced by deep reactive ion etching (DRIE) of silicon master molds on the UV-nanoimprint lithography (NIL) patterning of nanofeatures. The silicon molds were patterned with metasurface features with widths varying from 270 to 60 nm. This effect was studied by focus ion beam scanning electron microscopy (FIB-SEM) and atomic force microscopy (AFM). The Si loading etching effect is characterized by the variation of pattern feature depth concerning feature sizes because smaller features tend to etch more slowly than larger ones due to etchants being more difficult to pass through the smaller hole and byproducts being harder to diffuse out too. Thus, the NIL results obtained from the Si master mold contain different pattern geometries concerning pattern quality and residual photoresist layer thickness. The obtained results are pivotal for NIL for fabricating devices with various geometrical nanostructures as the research field moves towards commercial applications., Competing Interests: The authors declare no conflict of interest., (This journal is © The Royal Society of Chemistry.)

Despite important advances in the synthesis of inorganic perovskite nanocrystals (NCs), the long-term instability and degradation of their quantum yield (QY) over time need to be addressed to enable the further development and exploitation of these nanomaterials. Here we report stable CsPbI 3 perovskite NCs and their use in hybrid light emitting diodes (LEDs), which combine in one system the NCs and a blue GaN-based LED. Nanocrystals with improved morphological and optical properties are obtained by optimizing the post-synthesis replacement of oleic acid ligands with iminodibenzoic acid: the NCs have a long shelf-life (>2 months), stability under different environmental conditions, and a high QY, of up to 90%, in the visible spectral range. Ligand replacement enables the engineering of the morphological and optical properties of the NCs. Furthermore, the NCs can be used to coat the surface of a GaN-LED to realize a stable diode where they are excited by blue light from the LED under low current injection conditions, resulting in emissions at distinct wavelengths in the visible range. The high QY and fluorescence lifetime in the nanosecond range are key parameters for visible light communication, an emerging technology that requires high-performance visible light sources for secure, fast energy-efficient wireless transmission.