Journal
IEEE JOURNAL OF QUANTUM ELECTRONICS
Volume 47, Issue 5, Pages 636-641Publisher
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
DOI: 10.1109/JQE.2011.2107891
Keywords
AlGaInP; light emitting diode; waveguided light
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Funding
- National Science Council of China in Taiwan [NSC-98-2112-M-003-001-MY2]
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This paper describes a novel structure of an AlGaInP light-emitting diode (LED) to extract the waveguided light for high-brightness applications. Four devices are considered and compared. They are AlGaInP-sapphire LEDs with: 1) a planar Ag reflector (LED-A); 2) a patterned Ag reflector (LED-B); 3) a planar Ag reflector and surface-roughened features (LED-C); and 4) a patterned Ag reflector and surface-roughened features (LED-D). The patterned Ag reflector can be used to direct some of the waveguided light that bounces within the AlGaInP LED and sapphire substrate to the top escape cone of the LED surface. Additionally, the roughened features, which are randomly distributed on the LED surface, enable the waveguided light that is trapped inside the LED chip to be coupled efficiently into the air. As a result, the external quantum efficiencies of LED-A, LED-B, LED-C, and LED-D measured at I = 350 mA are eta = 9.20%, 10.46%, 15.22%, and 16.75%, respectively.
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