Optical cavity effects have a significant influence on the extraction efficiency of InGaN/GaN quantum-well-heterostructure flip-chip light-emitting diodes (FCLEDs). Light emitted from the quantum well (QW) self-interferes due to reflection from a closely placed reflective metallic mirror. These interference patterns couple into the escape cone and cause significant changes in the extraction efficiency as the distance between the QW and the metallic mirror varies. In addition, the radiative lifetime of the QW also changes as a function of the distance between the QW and the mirror surface. Experimental results from packaged FCLEDs, supported by optical modeling, show that a QW placed at a neighboring position corresponding to a minimum in overall light extraction. Furthermore, the optical model and experimental data are used to estimate the absolute internal quantum efficiency.
Power LEDs have evolved from simple indicators into illumination devices. For general lighting applications, where the objective is to light up an area, white LED arrays have been utilized to serve that function. Cost constraints will soon drive the industry to provide a discrete lighting solution. Early on, that will mean increasing the power densities while quantum efficiencies are addressed. For applications such as automotive headlamps & projection, where light needs to be tightly collimated, or controlled, arrays of die or LEDs will not be able to satisfy the requirements & limitations defined by etendue. Ultimately, whether a luminaire requires a small source with high luminance, or light spread over a general area, economics will force the evolution of the illumination LED into a compact discrete high power package. How the customer interfaces with this new package should be an important element considered early on in the design cycle. If an LED footprint of adequate size is not provided, it may prove impossible for the customer, or end user, to get rid of the heat in a manner sufficient to prevent premature LED light output degradation. Therefore it is critical, for maintaining expected LED lifetime & light output, that thermal performance parameters be defined, by design, at the system level, which includes heat sinking methods & interface materials or methdology.
High-power light-emitting diodes (LEDs) in both the AlInGaP (red to amber) and the AlGaInN (blue-green) material systems are now commercially available. These high-power LEDs enable applications wherein high flux is necessary, opening up new markets that previously required a large number of conventional LEDs. Data are presented on high-power AlGaInN LEDs utilizing flip-chip device structures. The high-power flip-chip LED is contained in a package that provides high current and temperature operation, high reliability, and optimized radiation patterns. These LEDs produce record powers of 350 mW (1A dc, 300 K) with low (<4V) forward voltages. The performance of these LEDs is demonstrated in terms of output power, efficiency, and electrical characteristics.
Michael Krames, G. Christenson, Dave Collins, Lou Cook, M. Craford, A. Edwards, Robert Fletcher, Nathan Gardner, Werner Goetz, William Imler, Eric Johnson, R. Scott Kern, Reena Khare, Frederick Kish, Chris Lowery, Mike Ludowise, Richard Mann, M. Maranowski, Steven Maranowski, Paul Martin, J. O'Shea, S. Rudaz, Dan Steigerwald, J. Thompson, Jonathan Wierer, Jingxi Yu, David Basile, Ying-Lan Chang, Ghulam Hasnain, M. Heuschen, Kevin Killeen, Christophe Kocot, Steven Lester, Jeffrey Miller, Gerd Mueller, Regina Mueller-Mach, S. Jeffrey Rosner, Richard Schneider, Tetsuya Takeuchi, Tun Tan
Currently, commercial LEDs based on AlGaInN emit light efficiently from the ultraviolet-blue to the green portion of the visible wavelength spectrum. Data are presented on AlGaInN LEDs grown by organometallic vapor phase epitaxy (OMVPE). Designs for high-power AlGaInN LEDs are presented along with their performance in terms of output power and efficiency. Finally, present and potential applications for high-power AlGaInN LEDs, including traffic signals and contour lighting, are discussed.
Conference Committee Involvement (4)
Fifth International Conference on Solid State Lighting
1 August 2005 | San Diego, California, United States
Fourth International Conference on Solid State Lighting
3 August 2004 | Denver, Colorado, United States
Third International Conference on Solid State Lighting
5 August 2003 | San Diego, California, United States
Light-Emitting Diodes: Research, Manufacturing, and Applications VII
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