Study of the Excitation Power Dependent Internal Quantum Efficiency in InGaN/GaN LEDs Grown on Patterned Sapphire Substrate

The mechanisms of the excitation power dependent internal quantum efficiency in InGaN/GaN multiple quantum wells (MQWs) LEDs grown on the planar and the patterned sapphire substrates (PSS) at temperature of 15 and 300 K were investigated. From observation the tendency of emission peak energy and car...

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Bibliographic Details
Published in:IEEE journal of selected topics in quantum electronics 2009-07, Vol.15 (4), p.1137-1143
Main Authors: Lee, Ya-Ju, Chiu, Ching-Hua, Ke, Chih Chun, Lin, Po Chun, Lu, Tien-Chang, Kuo, Hao-Chung, Wang, Shing-Chung
Format: Article
Language:English
Subjects:
Carriers
Density
Density measurement
Efficiency
Excitation
Gallium nitride
Gallium nitrides
GaN
Indium gallium nitrides
Internal quantum efficiency
Laser excitation
LED lamps
LEDs
Light emitting diodes
Quantum efficiency
Quantum well devices
Rough surfaces
Sapphire
Surface roughness
Temperature
Wavelength measurement
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Summary:The mechanisms of the excitation power dependent internal quantum efficiency in InGaN/GaN multiple quantum wells (MQWs) LEDs grown on the planar and the patterned sapphire substrates (PSS) at temperature of 15 and 300 K were investigated. From observation the tendency of emission peak energy and carrier lifetime variation in MQWs with different excitation power for both LED samples, we conclude the internal quantum efficiency would increase as coulomb screening effect dominates at lower carrier injection stage and decrease due to the band-filling effect at higher density stage. At room temperature, the majority of the initial injected carriers would be first consumed by the thermal activated nonradiative centers that hinder the further achievement of high-efficiency LED devices. Experimentally, the internal quantum efficiency of the LED grown on the PSS is ~70% and that of the LED grown on the planar sapphire substrate is ~62%. For the LED grown on the PSS, the observed higher internal quantum efficiency is due to the larger activation energy Therefore, the reduction of dislocation defects and the prevention of injected carriers escaping from extended states would be a promising prospective for InGaN/GaN MQWs LEDs to achieve high internal quantum efficiency.
ISSN:1077-260X
1558-4542
DOI:10.1109/JSTQE.2009.2014967