Project Lighting - April 2008 - (Page 10)

FeAtURe FIg 1 SimPlifieD 3-D aton StructureS are encaSeD in lumineScent material, aBout 50% coVereD With PhoSPhor (a) anD totally coVereD (B). helps to unravel failures and inadequacies of the LED design by showing current crowding and spreading, recombination traps, and design flaws that are not apparent or cannot be measured by experiment (either directly or indirectly). Moreover, after the device structure is optimized, simulation lends itself to an examination of the sensitivity of output characteristics to the device structure, thereby providing a design-for-manufacturing (DFM) framework for LEDs. simuLator rEquirEmEnts FIg 2 gooD current SPreaDing iS eSSential to reDucing Photon aBSorPtion By the actiVe region. The development of a simulator for white-LED design and optimization must cover a range of electrical and optical phenomena. The electrical transport of holes and electrons requires the coupled solution of the Poisson, continuity, and thermal equations, together with associated mobility, recombination, and generation models, and special treatment of carrier scattering into the quantum wells (QWs). The photon production (spontaneous emission) and amplification (stimulated emission) processes within the QWs are carefully treated using advanced gain calculations. Blue-light emission necessitates the use of indium gallium nitride/gallium nitride (InGaN/GaN) QWs, and these further require the inclusion of polarization charge sheets and piezoelectric screening effects. These electrical transport simulations must then be intricately coupled to the optical domain. Due to the relatively large dimensions of LEDs (a few hundred microns across), ray optics approaches such as ray tracing are typically employed and accepted as valid optical solutions. Using a spectrally resolved ray tracing (proprietary to Synopsys) Contents Viewpoint Selecting HBLED Drivers for Lighting Apps Simulation Technique for Optimizing White-LED Design An Analytical Approach to Cooling HBLEDs Lighting News Home Page Product Training Module Online Ordering Suppliers Catalog 10 | Project lighting | aPr 08 http://digikey.com/ http://ad.doubleclick.net/clk;198717884;26055153;t http://ad.doubleclick.net/clk;198717989;26055167;e http://ad.doubleclick.net/clk;198717988;26055168;e http://ad.doubleclick.net/clk;198717986;26055170;v http://ad.doubleclick.net/clk;198717985;26055171;v

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Project Lighting - April 2008 Contents Viewpoint About Project Lighting Sponsor Simulation Technique for Optimizing White-LED Design An Analytical Approach to Cooling HBLEDs LED Lighting Needs Smarts to be Competitive Lighting News Enter to Win an iPhone Refernce Materials Lighting Quick Links

Project Lighting - April 2008

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