Study of GaN-Based Light-Emitting Diodes Grown on Chemical Wet-Etching-Patterned Sapphire Substrate With V-Shaped Pits Roughening Surfaces

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)...

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Bibliographic Details
Published in:Journal of lightwave technology 2008-06, Vol.26 (11), p.1455-1463
Main Authors: Ya-Ju Lee, Hao-Chung Kuo, Tien-Chang Lu, Shing-Chung Wang, Kar Wai Ng, Kei May Lau, Zu-Po Yang, Chang, A.S.-P., Shawn-Yu Lin
Format: Article
Language:English
Subjects:
Autocorrelation
Autocorrelation functions
Chemicals
Diffusers
Efficiency
Emissions
Epitaxial growth
Extraction
Gallium nitride
III-V semiconductor materials
Light
Light emitting diodes
light-emitting diodes (LEDs)
Optical computing
optical device fabrication
Photoluminescence
Pits
Quantum efficiency
Rough surfaces
Roughening
Sapphire
Surface roughness
Temperature measurement
Threading dislocations
Vanadium
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Summary: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 times 10 9 /cm 2 to 3.62 times 10 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.
ISSN:0733-8724
1558-2213
DOI:10.1109/JLT.2008.922151