Efficiency improvement of GaN-based LEDs with ITO texturing window layers using natural lithography

Ray-Hua Horng*, Shao Hua Huang, Chiao Chih Yang, Dong Sing Wuu

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

37 Scopus citations


In conventional GaN light-emitting diodes (LEDs), a significant gap exists between the internal and external efficiencies owing to the narrow escape cone for light in high refractive index semiconductors. In this paper, p-side-up GaN/sapphire LEDs with surface-textured indium-tin-oxide (ITO) window layers were investigated using natural lithography with polystyrene spheres as the etching mask. Under optimum etching conditions, the surface roughness of the ITO film can reach 140 nm, while the polystyrene sphere on the textured ITO surface is maintained at about 250-300 nm in diameter. The LEDs fabricated using the surface-textured ITO provided an output power that exceeded that of the planar-surface LED by about 30% and 40% at 20 and 400 mA current injection, respectively. After calculating, the extraction quantum efficiency of ITO/GaN LEDs with and without textured surface is 22.6% and 17.4%, respectively. There is about 5.3% improvement in the extraction quantum efficiency.

Original languageEnglish
Pages (from-to)1196-1200
Number of pages5
JournalIEEE Journal on Selected Topics in Quantum Electronics
Issue number6
StatePublished - 1 Nov 2006


  • GaN
  • Indium-tin oxide (ITO)
  • Light-emitting diode (LED)
  • Natural lithography
  • Surface texturing

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