We report on the performance of AlGaN-based deep ultraviolet light-emitting diodes (UV-LEDs) emitting at 265 nm grown on stripe-patterned high-temperature annealed (HTA) epitaxially laterally overgrown (ELO) aluminium nitride (AlN)/sapphire templates. For this purpose, the structural and electro-optical properties of ultraviolet-c light-emitting diodes (UVC-LEDs) on as-grown and on HTA planar AlN/sapphire as well as ELO AlN/sapphire with and without HTA are investigated and compared. Cathodoluminescence measurements reveal dark spot densities of 3.5 × 10 9    cm − 2 , 1.1 × 10 9    cm − 2 , 1.4 × 10 9    cm − 2 , and 0.9 × 10 9    cm − 2 in multiple quantum well samples on as-grown planar AlN/sapphire, HTA planar AlN/sapphire, ELO AlN/sapphire, and HTA ELO AlN/sapphire, respectively, and are consistent with the threading dislocation densities determined by transmission electron microscopy (TEM) and high-resolution X-ray diffraction rocking curve. The UVC-LED performance improves with the reduction of the threading dislocation densities (TDDs). The output powers (measured on-wafer in cw operation at 20 mA) of the UV-LEDs emitting at 265 nm were 0.03 mW (planar AlN/sapphire), 0.8 mW (planar HTA AlN/sapphire), 0.9 mW (ELO AlN/sapphire), and 1.1 mW (HTA ELO AlN/sapphire), respectively. Furthermore, Monte Carlo ray-tracing simulations showed a 15% increase in light-extraction efficiency due to the voids formed in the ELO process. These results demonstrate that HTA ELO AlN/sapphire templates provide a viable approach to increase the efficiency of UV-LEDs, improving both the internal quantum efficiency and the light-extraction efficiency.

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The erosion resistances of ethylene propylene diene monomer (EPDM) insulations are often inadequate for advanced solid rocket motor (SRM) applications. EPDM modification by blending secondary matrixes is a feasible approach to improve the ablative properties of EPDM insulations. The addition of flexible inorganic hybrid rubbers as a secondary matrix, such as silicones and polyphosphazenes, may impart EPDM insulations with better ablative performance. The blends of EPDM/hybrid rubbers represent the state-of-the-art heat-shielding materials for SRM. In the present work, methyl-phenyl silicone/EPDM and poly(diaryloxyphosphazene)/EPDM insulation systems with various blending ratios of secondary matrixes have been prepared. The ablative properties of the insulations were examined by oxy-acetylene ablation tests, and the results showed that these properties could be enhanced accordingly by blending with hybrid rubbers under appropriate proportions. The unique charred layers resulting from the hybrid rubbers contributed to their excellent ablation properties. For example, the silicone/EPDM insulations exhibited a more significant improvement of ablation resistance properties. With a 1:1 blending ratio of silicone/EPDM, the linear ablation rate was 0.06 mm s−1 after 20 s of oxy-acetylene ablation. The enhancement in the ablative resistance was attributed to the charred layers with bunches of embedded compact microtubes with a length of 2–3 mm, which consisted of silicon carbide, silicon dioxide, and Si–O–C ceramics.

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