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Slender springtails (Entomobrya nivalis) and orange springtails (Neanura muscorum) are capable of repelling water and organic liquids using the hexagonally arranged nanoscale waxy protrusions and microscale wrinkles on their cuticles to protect the skin-breathing arthropods against suffocation in diversified survival environments. The omniphobic hierarchical structures can even shed and directionally transport liquids along the longitudinal direction of the wrinkles. Bioinspired by springtails, monolayer colloidal crystals are self-assembled onto anisotropic microwrinkled substrates and serve as structural templates to pattern antiwetting hierarchical structure arrays. The dependence of structure configuration on the antiwetting performances is systematically investigated in this study. Impressively, the optimized structure array exhibits anisotropic omniphobic sliding characteristics toward liquids with varied surface tensions ranging from 72.8 to 27.2 mN/m. The springtail-inspired coatings undoubtedly have great potential for developing innovative applications that require directional transportation and the collection of liquids. [ABSTRACT FROM AUTHOR]

InGaN resonant-cavity light-emitting diodes (RC-LEDs) with a dielectric distributed Bragg reflector (DBR), a porous-GaN DBR, and a nitrogen ion (N+)-implanted aperture (6 μm diameter) were demonstrated. In the ion implantation process, the N+ ions were penetrated directly through an indium-tin-oxide conductive layer and SiO2 layer to form the insulated p-GaN:Mg layer, which provides a fascinating current confinement structure. The broadened electroluminescence (EL) peaks were measured at 401.5 and 435.8 nm in the implanted LED without double DBR structures. Multiple EL emission peaks with narrow line widths were observed in the RC-LED structure, indicating a strong resonant effect with different cavity modes. Two groups of effective resonant-cavity lengths, 1.48 and 1.50 μm, were analyzed through the angle-resolved EL spectra due to the anisotropic porous-GaN layers in the porous DBR structure. The divergent angles in far-field EL radiation patterns were reduced from 118° for the nontreated LED to 28° for the RC-LED structures. A high resonant-cavity effect, line-width narrowing phenomenon, and small divergent angle were observed in the InGaN RC-LED with 6 μm-diameter ion-implanted aperture and top dielectric/bottom porous DBR structures. [ABSTRACT FROM AUTHOR]

A porous-Al0.47GaN/n-Al0.47GaN stack structure with a large refractive index contrast has been fabricated through a homoepitaxial growth process on a Si-doped n+-Al0.47GaN/n-Al0.47GaN stack structure with a simple electrochemical wet etching process. A 20-pairs porous-Al0.47GaN distributed Bragg reflector structure (DBR) with a high aluminum content was fabricated at the deep-ultraviolet wavelength region of light emitting diodes. Low compressive strain and high reflectance has been observed in a porous-AlGaN/n-AlGaN DBR structure with 93% reflectivity at 276 nm. The high reflectance spectrum was measured at the 265 to 287 nm wavelength region in the porous AlGaN DBR structure. The absorption wavelength of the AlGaN layer was observed at about 250 nm, which is shorter than the high reflectance wavelength region of the porous DBR. Light extraction efficiency of the deep-UV optoelectronic devices can be improved by integrating the embedded porous AlGaN reflectors during the epitaxial growth process. [ABSTRACT FROM AUTHOR]

The integration of light-emitting diodes (LEDs) into the flexible devices has exhibited a great potential in the next-generation consumer electronics. In this study, we have demonstrated an exfoliated InGaN nanomembrane LED (NM-LED) separated from a GaN/sapphire substrate through an electrochemically wet etching process. The peak wavelengths blue-shifted phenomenon of the photoluminescence (PL) and the electroluminescence spectra were observed on the free-standing NM-LED compared to the nontreated LED with the same structure, which can be ascribed to the partial strain relaxation of the LED structure confirmed by the Raman spectra and the X-ray diffraction curves. A small divergent angle of the PL emission light has also been observed on the NM-LED. Moreover, the peak emission wavelength of this NM-LED can be even modulated from a red shift (521.7 nm) to a blue shift (500.4 nm) compared with that of the flat state (509.4 nm) while being curved convexly from top p-GaN:Mg side to bottom n-GaN:Si side. Our study provides an elegant way to develop a bendable light source with variable emission wavelengths through the mechanical deformation method.

We report here a simple and robust process to convert embedded conductive GaN epilayers into insulating GaOx and demonstrate its efficacy in vertical current blocking and lateral current steering in a working LED device. The fabrication processes consist of laser scribing, electrochemical (EC) wet-etching, photoelectrochemical (PEC) oxidation, and thermal oxidization of a sacrificial n(+)-GaN:Si layer. The conversion of GaN is made possible through an intermediate stage of porosification where the standard n-type GaN epilayers can be laterally and selectively anodized into a nanoporous (NP) texture while keeping the rest of the layers intact. The fibrous texture of NP GaN with an average wall thickness of less than 100 nm dramatically increases the surface-to-volume ratio and facilitates a rapid oxidation process of GaN into GaOX. The GaOX aperture was formed on the n-side of the LED between the active region and the n-type GaN layer. The wavelength blueshift phenomena of electroluminescence spectra is observed in the treated aperture-emission LED structure (441.5 nm) when compared to nontreated LED structure (443.7 nm) at 0.1 mA. The observation of aperture-confined electroluminescence from an InGaN LED structure suggests that the NP GaN based oxidation will play an enabling role in the design and fabrication of III-nitride photonic devices.