Performance enhancement of GaN-based flip-chip ultraviolet light-emitting diodes with a RPD AlN nucleation layer on patterned sapphire substrate

B. C. Lin, C. H. Chiu*, C. Y. Lee, H. V. Han, P. M. Tu, T. P. Chen, Z. Y. Li, Po-Tsung Lee, Chien-Chung Lin, G. C. Chi, C. H. Chen, B. Fan, C. Y. Chang, Hao-Chung Kuo

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

In this work, flip-chip ultraviolet light-emitting diodes (FCUVLEDs) on patterned sapphire substrate (PSS) at 375 nm were grown by an atmospheric pressure metal organic chemical vapor deposition (APMOCVD). A specialized reactive plasma deposited (RPD) AlN nucleation layer was utilized on the PSS to enhance the quality of the epitaxial layer. By using high-resolution X-ray diffraction, the full-width at half-maximum of the rocking curve shows that the FCUV-LEDs with RPD AlN nucleation layer had better crystalline quality when compared to conventional GaN nucleation samples. From the transmission electron microscopy (TEM) image, it can be observed that the tip and incline portion of the pattern was smooth using the RPD AlN nucleation layer. The threading dislocation densities (TDDs) are reduced from 7 × 10 7 cm -2 to 2.5 × 10 7 cm -2 at the interface between the u-GaN layers for conventional and AlN PSS devices, respectively. As a result, a much higher light output power was achieved. The improvement of light output power at an injection current of 20 mA was enhanced by 30%. Further photoluminescence measurement and numerical simulation confirm such increase of output power can be attributed to the improvement of material quality and light extraction.

Original languageEnglish
Pages (from-to)1632-1640
Number of pages9
JournalOptical Materials Express
Volume4
Issue number8
DOIs
StatePublished - 1 Aug 2014

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