Title: Study of GaN-based light-emitting diodes grown on chemical wet-etching-patterned sapphire substrate with V-shaped pits roughening surfaces
Authors: Lee, Ya-Ju
Kuo, Hao-Chung
Lu, Tien-Chang
Wang, Shing-Chung
Ng, Kar Wai
Lau, Kei May
Yang, Zu-Po
Chang, Allan Shih-Ping
Lin, Shawn-Yu
Department of Photonics
Keywords: epitaxial growth;light-emitting diodes (LEDs);optical device fabrication
Issue Date: 1-May-2008
Abstract: 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 x10(9)/cm(2) to 3.62 x10(8)/cm(2), 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.
URI: http://dx.doi.org/10.1109/JLT.2008.922151
ISSN: 0733-8724
DOI: 10.1109/JLT.2008.922151
Volume: 26
Issue: 9-12
Begin Page: 1455
End Page: 1463
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