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Microscopic photoluminescence was applied to investigate μm-order inhomogeneity of InGaN alloys. Samples had InGaN/GaN multiple-quantum-well structures grown on sapphire substrates at various temperatures, and luminescence was adjusted to be green. Luminescence morphologies of dendritic appearance were observed on as-grown samples. Bright spots luminescing at long wavelengths (green to amber) were formed at high growth temperatures. After annealing at 1000°C, the bright spots disappeared and the dendritic morphology turned into a granular morphology. Because of these μm-order inhomogeneities, it has been suggested that small-scale characterization (sub-μm or smaller) requires special attention in order not to miss effects of μm-order inhomogeneity in InGaN alloys.

Substituted indoles are important as drugs. A number of valuable indoles have been synthesized via nucleophilic substitution at the 3'‐position of indoles. However, the preparation of an indolylmethyl electrophile containing a tertiary carbon at the 3'‐position and its subsequent nucleophilic substitution are challenging owing to the instability of the electrophile. Herein, we demonstrated the rapid one‐flow synthesis of indoles via sequential 1,2‐addition/nucleophilic substitution of indolyl‐3‐carbaldehydes. The use of a microflow technology helped in suppressing the undesired reactions caused by the unstable intermediates, resulting in significantly higher yields and reproducibility compared to those under batch conditions. A crown ether was effective when 1‐alkylindole‐3‐carboxaldehyde was used as a substrate. However, the crown ether exerted a detrimental effect when 1H‐indole‐3‐carboxaldehyde was used. A total of 15 structurally diverse indole derivatives were obtained in generally acceptable to good yields. [ABSTRACT FROM AUTHOR]

Light extraction from two-dimensional objects is discussed. Analytical calculations in terms of three different parameters have been applied to equiangular polygons to trace light rays during multiple reflections in a polygon. Based on the result that there are a finite number of incident angles in a polygon for a light ray, it was found that the triangle has the least chance to trap light rays among the polygons. The discussion has been extended to parallelograms, which have an advantage in light extraction to rectangles. Placement of a possible light source in polygons is discussed. OCIS codes: 250.0250, 160.6000.

A metal layer formed on the backside of InGaN/sapphire-based light-emitting diodes deteriorates the inherent optical power output. An experimental approach of a suspended die is employed to study the effects of such metal layers via a direct comparison in radiant flux from a discrete die with and without a reflector. A sphere package that employs no reflector is proposed and fabricated. Light extraction of the sphere design is discussed; a light source in the sphere package would not have to be either an ideal point or placed at the center of the sphere, due to a finite critical angle at the sphere/air interface. OCIS codes: 230.3670, 160.6000.