Study of GaN-based light-emitting diodes grown on chemical wet-etching-patterned sapphire substrate with V-shaped pits roughening surfaces

Ya-Ju Lee, Hao Chung Kuo, Tien Chang Lu, Shing Chung Wang, Kar Wai Ng, Kei May Lau, Zu Po Yang, Allan Shih Ping Chang, Shawn Yu Lin

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29 Citations (Scopus)


We investigate the mechanism responding for performance enhancement of gallium nitride (GaN)-based light-emitting diode (LED) grown on chemical wet-etching-patterned sapphire substrate (CWE-PSS) with V-Shaped pit features on the top surface. According to temperature-dependent photoluminescence (PL) measurement and the measured external quantum efficiency, the structure can simultaneously enhance both internal quantum efficiency and light extraction efficiency. Comparing to devices grown on planar sapphire substrate, the threading dislocation defects of LED grown on CWE-PSS are reduced from 1.28 × 109/ cm2 to 3.62 × 108/cm, leading to a 12.5% enhancement in internal quantum efficiency. In terms of the theoretical computing of radiation patterns, the V-Shaped pits roughening surface can be thought of as a strong diffuser with paraboloidal autocorrelation function, increasing the escape probability of trapped photons and achieving a 20% enhancement in light extraction efficiency. Moreover, according to the measurement of optical diffraction power, CWE-PSS demonstrated superior guided light extraction efficiency than that of planar sapphire substrate, thus an extra 7.8% enhancement in light extraction efficiency was obtained. Therefore, comparing to the conventional LED, an overall 45% enhancement in integrated output power was achieved.

Original languageEnglish
Pages (from-to)1455-1463
Number of pages9
JournalJournal of Lightwave Technology
Issue number11
Publication statusPublished - 2008 Jun 1



  • Epitaxial growth
  • Light-emitting diodes (LEDs)
  • Optical device fabrication

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

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