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LED manufacturing This technology is available for licensing.
Detailed Technology Description
Researchers at the University of California, Santa Barbara have developed new LED structures that provide increased light extraction efficiency while retaining a planar structure. The new LED structures provide direct emissions outside the structure and, in addition, convert guided light into extracted light using a diffraction grating. This grating may be placed outside the current-injected region of the active layer, or current may be injected into the grating region. Moreover, the diffraction grating is comprised of an array of holes, which may be pierced into the emitting species of the active layer, or only in other layers of the LED. The diffraction grating is a two-dimensional photonic crystal extractor, and the present invention provides improvements over previous implementations of photonic crystal extractors. The efficiency of the new LED structure is due to the fact that guided light is only (or mostly) emitted into guided modes that will be interacting with the photonic crystal, so that the many guided modes that are usually lost are diffracted outside the device. This is especially important in the case of an LED that supports numerous guided modes, such as a nitride-materials-based LED (which usually has to be several microns thick due to material growth considerations). The new LED structure retains a planar single layer structure making it easily manufacturable at low cost.
Supplementary Information
Patent Number: US7582910B2 Application Number: US200567956A Inventor: David, Aurelien J. F. | Weisbuch, Claude C. A. | DenBaars, Steven P. Priority Date: 28 Feb 2005 Priority Number: US7582910B2 Application Date: 28 Feb 2005 Publication Date: 1 Sep 2009 IPC Current: H01L002715 | H01L003112 | H01L003320 US Class: 257086 | 257094 | 257098 | 257103 Assignee Applicant: The Regents of the University of California Title: High efficiency light emitting diode (LED) with optimized photonic crystal extractor Usefulness: High efficiency light emitting diode (LED) with optimized photonic crystal extractor Summary: for use in liquid crystal display (LCD). Novelty: Light emitting diode for use in liquid crystal display, has several optical confinement layers with multiple diffraction grating having photonic crystals
Industry
Optics
Sub Group
LED/OLED
Application No.
7582910
Others
Background
As semiconductor materials have improved, the efficiency of semiconductor devices has also improved and new wavelength ranges have been used. Gallium nitride (GaN) based light emitters are probably the most promising for a variety of applications. GaN provides efficient illumination in the ultraviolet (UV) to amber spectrum, when alloyed with varying concentrates of indium (In), for example. Unfortunately, most of the light emitted within a semiconductor LED material is lost due to total internal reflection at the semiconductor-air interface. Typical semiconductor materials have a high index of refraction, and thus, according to Snell's law, most of the light will remain trapped in the materials, thereby degrading efficiency. By choosing a suitable geometry for the LED, a higher extraction efficiency can be achieved.
