Structural analysis of nitride-based LEDs grown on micro- and nano-scale patterned sapphire substrates

The structural properties of nitride-based light-emitting diodes (LEDs) grown on micro-and nano-scale patterned sapphire substrates (PSS) were discussed in detail. The high resolution X-ray diffraction (HRXRD) and etch-pit density (EPD) results reveal that the crystalline quality of the epitaxial GaN film could be effectively improved by using the PSS technique, and depended on the aspect ratio of PSS. The crystalline quality of epitaxial GaN films grown on PSS-2 mu m and PSS-3 mu m was better than that of the LED grown on NPSS. The electrical characteristics and junction temperature results of the LED grown on micro-scale PSS were better compared with nano-scale PSS. But the output power of the LED grown on nano-scale PSS was larger than that of the LED grown on micro-scale PSS since the pattern-size of PSS is related to the capability of light extraction. However, when the spacing of PSS is less than 2 mu m, some voids formed at the GaN/sapphire interface may cause the thermal dissipation problem of LEDs. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim