A5002309846- GaN-based semiconductor devices and materials
- Semiconductor Quantum Structures and Devices
- Semiconductor Lasers and Optical Devices
- Ga2O3 and related materials
- Semiconductor materials and devices
- Photonic and Optical Devices
- Luminescence Properties of Advanced Materials
- Photocathodes and Microchannel Plates
- ZnO doping and properties
- Color Science and Applications
- Perovskite Materials and Applications
- Gas Sensing Nanomaterials and Sensors
- Metal and Thin Film Mechanics
- Color perception and design
- Organic Light-Emitting Diodes Research
- Photonic Crystals and Applications
- Acoustic Wave Resonator Technologies
- Quantum Dots Synthesis And Properties
- Spectroscopy and Laser Applications
- Impact of Light on Environment and Health
- Hydrogen's biological and therapeutic effects
- Nanowire Synthesis and Applications
- Advanced Chemical Physics Studies
- Electronic and Structural Properties of Oxides
- Advanced Fiber Laser Technologies
Soraa (United States)
2010-2015
Philips (United States)
2007-2009
Philips (United Kingdom)
2009
Philips (Finland)
2006-2009
Trimble (United States)
1998-2008
Agilent Technologies (United States)
2000-2005
Lighting Innovation (United States)
2000-2004
Hewlett-Packard (United States)
1998-2003
University of Sheffield
2003
University of Illinois Urbana-Champaign
1993-1995
Status and future outlook of III-V compound semiconductor visible-spectrum light-emitting diodes (LEDs) are presented. Light extraction techniques reviewed efficiencies quantified in the 60%+ (AlGaInP) ~80% (InGaN) regimes for state-of-the-art devices. The phosphor-based white LED concept is recent performance discussed, showing that high-power LEDs now approach 100-lm/W regime. Devices employing multiple phosphors "warm" color temperatures (~3000-4000 K) high rendering (CRI>80), which...
The Auger recombination coefficient in quasi-bulk InxGa1−xN (x∼9%–15%) layers grown on GaN (0001) is measured by a photoluminescence technique. samples vary InN composition, thickness, and threading dislocation density. Throughout this sample set, the ranges from 1.4×10−30to2.0×10−30cm6s−1. authors argue that an of magnitude, combined with high carrier densities reached blue green InGaN∕GaN quantum well light-emitting diodes (LEDs), reason why maximum external efficiency these devices...
Abstract The development and demonstration of a highly efficient warm‐white all‐nitride phosphor‐converted light emitting diode (pc‐LED) is presented utilizing GaN based quantum well blue LED two novel nitrogen containing luminescent materials, both which are doped with Eu 2+ . For color conversion the primary nitridosilicates M 2 Si 5 N 8 (orange‐red) MSi O (yellow‐green), = alkaline earth, were employed, thus achieving high luminous efficiency (25 lumen/W at 1 W input), excellent quality...
A truncated-inverted-pyramid (TIP) chip geometry provides substantial improvement in light extraction efficiency over conventional AlGaInP/GaP chips of the same active junction area (∼0.25 mm2). The TIP decreases mean photon path-length within crystal, and thus reduces effects internal loss mechanisms. By combining this improved device with high-efficiency multiwell layers, record-level performance for visible-spectrum light-emitting diodes is achieved. Peak efficiencies exceeding 100 lm/W...
Phosphor conversion of light-emitting diode light for white sources and some monochrome applications requires particular phosphor properties has to take into account specific issues if aimed at high-power output. Limitations solutions will be discussed, giving special considerations drive temperature dependencies. Efficiencies 32 lm/W with good color rendering 4600 K 35 green (535 nm) have been demonstrated.
Auger recombination is determined to be the limiting factor for quantum efficiency InGaN–GaN (0001) light-emitting diodes (LEDs) at high current density. High-power double-heterostructure (DH) LEDs are grown by metal-organic chemical vapor deposition. By increasing active layer thickness, DH can reach a maximum in densities above 200A∕cm2. Encapsulated thin-film flip-chip with peak wavelength of 432nm have an external 40% and output power 2.3W 2A.
Data are presented on high-power AlGaInN flip-chip light-emitting diodes (FCLEDs). The FCLED is “flipped-over” or inverted compared to conventional (LEDs), and light extracted through the transparent sapphire substrate. This avoids absorption from semitransparent metal contact in epitaxial-up designs. power has a large emitting area (∼0.70 mm2) an optimized contacting scheme allowing high current (200–1000 mA, J∼30–143 A/cm2) operation with low forward voltages (∼2.8 V at 200 mA), therefore...
Abstract Solid‐state lighting is a rapidly evolving, emerging technology whose efficiency of conversion electricity to visible white light likely approach 50% within the next several years. This significantly higher than that traditional technologies, giving solid‐state potential enable significant reduction in rate world energy consumption. Further, there no fundamental physical reason why efficiencies well beyond could not be achieved, which even more usage. In this article, we discuss...
Electrical operation of InGaN/GaN quantum-well heterostructure photonic crystal light-emitting diodes (PXLEDs) is demonstrated. A triangular lattice formed by dry etching into the top GaN layer. Light absorption from metal contact minimized because layers are engineered to provide lateral current spreading, allowing carrier recombination proximal yet displaced contact. The chosen spacing for causes Bragg scattering guided modes out LED, increasing extraction efficiency. far-field radiation...
The history of development for gallium-nitride-based light-emitting diodes (LEDs) is reviewed. We identify two broad developments in GaN-based LED technology: first, the key breakthroughs that enabled devices on foreign substrates like sapphire (first-generation LEDs), and, second, a new wave benefiting from GaN substrate manufacturing, which has led to native bulk-GaN-based LEDs with unprecedented performance characteristics portend disruptive shift output power density and corresponding...
We study the carrier distribution in multi quantum well (multi-QW) InGaN light-emitting diodes. Conventional wisdom would assume that a large number of QWs lead to smaller density per QW, enabling efficient recombination at high currents. use angle-resolved far-field measurements determine location spontaneous emission series multi-QW samples. They reveal that, no matter how many are grown, only QW nearest p layer emits light under electrical pumping, which can limit performances high-power devices.
Data are presented on the operation of thin-film flip-chip InGaN∕GaN multiple-quantum-well light-emitting diodes (LEDs). The combination LED concept with technology is shown to provide surface brightness and flux output advantages over conventional vertical-injection LEDs. Performance characteristics blue, white, green 1×1mm2 LEDs described. Blue (∼441nm) demonstrated radiance 191mW∕mm2sr at 1A drive, more than two times brighter An encapsulated blue lamp have external quantum efficiency 38%...
We report on violet-emitting III-nitride light-emitting diodes (LEDs) grown bulk GaN substrates employing a flip-chip architecture. Device performance is optimized for operation at high current density and temperature, by specific design consideration the epitaxial layers, extraction efficiency, electrical injection. The power conversion efficiency reaches peak value of 84% 85 °C remains density, owing to low current-induced droop series resistance.
In a practical sense, the development of high-performance visible-spectrum light-emitting diodes (LEDs) has occurred over period 60 years, beginning with discovery first semiconductor p-n junction in 1940, solid-state electronic band theory 1940s, invention bipolar transistor 1947, and demonstration efficient light generation from III-V alloys 1950s 1960s. This paper reviews some major scientific technological developments observations that have created materials device technologies...
High power light emitting diodes (LEDs) continue to increase in output flux with the best III-nitride based devices today over 150 lm of white, cyan, or green light. The key design features such products will be covered special emphasis on packaging, flip-chip device design, and phosphor coating technology. high-flux performance these is enabling many new applications for LEDs. Two most interesting are LCD display backlighting vehicle forward lighting. advantages LEDs competing lighting...
InGaN – GaN multiple-quantum-well light-emitting diodes were fabricated on (101¯0) m plane films grown 4H–SiC substrates. The [0001] axis of the epitaxial film is parallel to substrate. surface striated, with features running perpendicular c and a maximum height difference 45nm. Electroluminescence shows strong polarization anisotropy, 7× more light emitted compared axis. An Ahrrenius fit ratio indicates that there 49meV in energy gap between two states. This suggests high can be maintained...
We present experimental results on III–nitride light-emitting diodes emitting at 410 nm, grown low-defectivity bulk GaN substrates. The epitaxial layers are optimized for high peak efficiency and maintain very current densities. use a volumetric device architecture with surface roughness to maximize light extraction efficiency. report an external quantum of 68% 180 A cm−2. No crowding is observed density. also demonstrate flat-line reliable operation over 1000 h.
Commercial lighting for ambient and display applications is mostly based on blue light-emitting diodes (LEDs) combined with phosphor materials that convert some of the light into green, yellow, orange, red. Not many can offer stable output under high incident intensities thousands operating hours. Even most promising LED phosphors saturate in high-power applications, is, they show decreased output. The saturation behavior often poorly understood. Here, we review three popular commercial materials, Y
Surface recombination is an important characteristic of optoelectronic material. Although surface a limiting factor for very small devices it has not been studied intensively. We have investigated velocity on the exposed surfaces AlGaN, InGaAs, and InGaAlP material systems by using absolute photoluminescence quantum efficiency measurements. Two these three low enough to be usable in nanoscale photonic crystal light-emitting diodes.
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 quantum well (QW) self-interferes due to reflection closely placed reflective metallic mirror. The interference patterns couple into escape cone for light FCLED. This effect causes changes in as distance between QW and mirror varies. In addition, radiative lifetime also function surface. Experimental results...
The performance of liquid crystal displays and micro display projection systems is for a large part determined by the lamps illumination optics they are using. Traditionally, gas discharge used, but light-emitting diode gradually taking over because their attractive characteristics. We will discuss how transfer to diodes in various architectures changes key parameters, remaining technical challenges, prospects future improvement
We have designed and implemented a monolithic, dual-wavelength blue/green light emitting diode (LED) consisting of two active indium gallium nitride/gallium nitride (InGaN/GaN) multiple-quantum-well segments. The segments are part single vertical epitaxial structure in which p++/n++ InGaN/GaN tunnel junction is inserted between the LEDs, this proof-of-concept device at 470 nm 535 nm, respectively. has been operated as three-terminal with independent electrical control each LEDs to nanosecond...
The performance of high-power AlInGaN light emitting diodes (LEDs) is characterized by output–current–voltage (L–I–V) measurements for devices with peak emission wavelengths ranging from 428 to 545 nm. highest external quantum efficiency (EQE) measured short wavelength LEDs (428 nm) at ≈29%. EQE decreases increasing wavelength, reaching ≈13% 527 With low forward voltages ≈3.3 ≈2.9 V a drive current density 50 A/cm2, these exhibit power conversion efficiencies ≈26% ≈10% (527 nm).