Efficiency improvement of near-ultraviolet InGaN LEDs using patterned sapphire substrates

Woei Kai Wang*, Dong Sing Wuu, Shu Hei Lin, Pin Han, Ray-Hua Horng, Ta Cheng Hsu, Donald Tai Chan Huo, Ming Jiunn Jou, Yuan Hsin Yu, Aikey Lin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

72 Scopus citations


The use of conventional and patterned sapphire substrates (PSSs) to fabricate InGaN-based near-ultraviolet (410 nm) light-emitting diodes (LEDs) was demonstrated. The PSS was prepared using a periodic hole pattern (diameter: 3 μm; spacing: 3 μn) on the (0001) sapphire with different etching depths. From transmission-electron-microscopy and etch-pit-density studies, the PSS with an optimum pattern depth (Dh = 1.5 μm) was confirmed to be an efficient way to reduce the thread dislocations in the GaN microstructure. It was found that the output power increased from 8.6 to 10.4 mW, corresponding to about 29% increases in the external quantum efficiency. However, the internal quantum efficiency (20 mA) was about 36% and 38% for the conventional and PSS LEDs, respectively. The achieved improvement of the output power is not only due to the improvement of the internal quantum efficiency upon decreasing the dislocation density, but also due to the enhancement of the extraction efficiency using the PSS. Finally, better long-time reliability of the PSS LED performance was observed.

Original languageEnglish
Pages (from-to)1403-1409
Number of pages7
JournalIEEE Journal of Quantum Electronics
Issue number11
StatePublished - 1 Nov 2005


  • GaN
  • InGaN
  • Light-emitting diode (LED)
  • Near ultraviolet (UV)
  • Patterned sapphire substrate (PSS)

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