AlGaN-based deep ultraviolet light-emitting diodes grown on nano-patterned sapphire substrates with significant improvement in internal quantum efficiency

We report high-performance AlGaN-based deep ultraviolet light-emitting diodes grown on nano-patterned sapphire substrates (NPSS) using metal - organic chemical vapor deposition. By nanoscale epitaxial lateral overgrowth on NPSS, 4-mu m AIN buffer layer has shown strain relaxation and a coalescence thickness of only 2.5 mu m. The full widths at half-maximum of X-ray diffraction (002) and (102) omega-scan rocking curves of AlN on NPSS are only 694 and 319.1 arcsec. The threading dislocation density in AlGaN-based multi-quantum wells, which are grown on this AIN/NPSS template with a light-emitting wavelength at 283 nm at room temperature, is reduced by 33% compared with that on flat sapphire substrate indicated by atomic force microscopy measurements, and the internal quantum efficiency increases from 30% to 43% revealed by temperature-dependent photoluminescent measurement. (C) 2014 Elsevier B.V. All rights reserved.