AVS 52nd International Symposium
    Science of Semiconductor White Light Topical Conference Monday Sessions
       Session WL-MoA

Invited Paper WL-MoA1
Improving the Brightness of GaN-based Light Emitting Diodes in the Green

Monday, October 31, 2005, 2:00 pm, Room 310

Session: Science of Semiconductor White Lighting
Presenter: C. Wetzel, Rensselaer Polytechnic Institute
Authors: C. Wetzel, Rensselaer Polytechnic Institute
T. Detchprohm, Rensselaer Polytechnic Institute
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Technological innovations to address impeding energy cost raises are of high priority for global economics. Generating white light without the heating losses of light bulbs by means of semiconductor light emitting devices is a prime opportunity to reduce the energy consumption for lighting -- about 20% of the total energy consumption in the US -- by an estimated 28%. Alloys of GaInN offer the prospect for high power light emitters across the entire visible spectrum. While high performance red LEDs have been developed in AlGaInP materials, blue GaInN LEDs have shown major progress in recent years. The immediate challenge is to increase performance throughout the green from 520 nm to 550 nm. Based on detailed spectroscopic bandstructure characterization of GaInN/GaN alloys and quantum wells we have identified materials and device design parameters for high power LED dies emitting in this range. We developed a production scale epitaxial growth process by metal organic vapor phase epitaxy for 525 nm dominant wavelength at typical 1.7 mW at 20 mA in (350 µm)@super 2@ dies. In a (400 µm)@super 2@ design we reach values of 2.5 mW in unencapsulated die. This corresponds to 5.0 mW upon proper encapsulation and 6 to 8 mW for flip-chip processed devices. We provide an analysis of the performance limitations imparting further development towards higher power and higher efficiency devices. Despite respectable performance there is ample of headroom for improvement in the internal light generation efficiency which furthermore can be enhanced by improvements to the light extraction. We present our approach within the framework of significant future energy savings by solid state white light generation.