Defect reduction and efficiency improvement of near-ultraviolet emitters via laterally overgrown GaN on a GaN/patterned sapphire template

D. S. Wuu*, W. K. Wang, K. S. Wen, S. C. Huang, S. H. Lin, S. Y. Huang, C. F. Lin, Ray-Hua Horng

*Corresponding author for this work

Research output: Contribution to journalArticle

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Abstract

An approach to improve the defect density and internal quantum efficiency of near-ultraviolet emitters was proposed using a combination of epitaxial lateral overgrowth (ELOG) and patterned sapphire substrate (PSS) techniques. Especially, a complementary dot array pattern corresponding to the underlying PSS was used for the ELOG-Si O2 mask design. Based on the transmission-electron- microscopy and etch-pit-density results, the ELOGSi O2 GaNPSS structure can reduce the defect density to a level of 105 cm-2. The internal quantum efficiency of the InGaN-based ELOG-PSS light-emitting diode (LED) sample showed three times in magnitude as compared with that of the conventional GaN/sapphire one. Under a 20 mA injection current, the output powers of ELOG-PSS, PSS, and conventional LED samples were measured to be 3.3, 2.9, and 2.5 mW, respectively. The enhanced output power could be due to a combination of the reduction in dislocation density (by ELOG) and improved light extraction efficiency (by PSS). Unlike the previous double ELOG approaches, the presented ELOG-PSS structure needs only one regrowth process and will have high potential in future high-quality ultraviolet emitters, even blue/green laser diode applications.

Original languageEnglish
Article number161105
JournalApplied Physics Letters
Volume89
Issue number16
DOIs
StatePublished - 25 Oct 2006

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