Gallium nitride is a binary III/V direct bandgap semiconductor commonly used in blue light-emitting diodes since the 1990s. The compound is a very hard material that has a Wurtzite crystal structure. Its wide band gap of 3.4 eV affords it special properties for applications in optoelectronics, high-power and high-frequency devices. For example, GaN is the substrate that makes violet (405 nm) laser diodes possible, without requiring nonlinear optical frequency doubling.
Aluminium nitride (AlN) is a solid nitride of aluminium. It has a high thermal conductivity of up to 321 W/(m·K) and is an electrical insulator. Its wurtzite phase (w-AlN) has a band gap of ~6 eV at room temperature and has a potential application in optoelectronics operating at deep ultraviolet frequencies.
A blue laser emits electromagnetic radiation with a wavelength between 400 and 500 nanometers, which the human eye sees in the visible spectrum as blue or violet.
Indium gallium nitride is a semiconductor material made of a mix of gallium nitride (GaN) and indium nitride (InN). It is a ternary group III/group V direct bandgap semiconductor. Its bandgap can be tuned by varying the amount of indium in the alloy. InxGa1−xN has a direct bandgap span from the infrared for InN to the ultraviolet of GaN. The ratio of In/Ga is usually between 0.02/0.98 and 0.3/0.7.
Nichia Corporation is a Japanese chemical engineering and manufacturing company headquartered in Anan, Japan with global subsidiaries. It specializes in the manufacturing and distribution of phosphors, including light-emitting diodes (LEDs), laser diodes, battery materials, and calcium chloride.
Isamu Akasaki was a Japanese engineer and physicist, specializing in the field of semiconductor technology and Nobel Prize laureate, best known for inventing the bright gallium nitride (GaN) p-n junction blue LED in 1989 and subsequently the high-brightness GaN blue LED as well.
Sir Colin John Humphreys is a British physicist and a hobbyist Bible scholar. He is the Professor of Materials Science at Queen Mary University of London.
George Andrew Davidson Briggs is a British scientist. He is Professor of Nanomaterials in the Department of Materials at the University of Oxford. He is best known for his early work in acoustic microscopy and his current work in materials for quantum technologies.
Hiroshi Amano is a Japanese physicist, engineer and inventor specializing in the field of semiconductor technology. For his work he was awarded the 2014 Nobel Prize in Physics together with Isamu Akasaki and Shuji Nakamura for "the invention of efficient blue light-emitting diodes which has enabled bright and energy-saving white light sources".
Steven P. DenBaars is an American material scientist, electrical engineer, and academic. He is a professor of Materials and Electrical and Computer Engineering, and the executive director of the Solid State Lighting and Energy Electronics Center at the University of California, Santa Barbara. He is also a Fellow of National Academy of Inventors (NAI), and was selected as a Member of National Academy of Engineering (NAE) in 2012 for contributions to gallium nitride-based materials and devices for solid state lighting and displays.
Magdalena (Magda) Titirici is a Professor of Sustainable Energy Materials at Imperial College London.
Ruth Cameron FInstP FIOM3 FREng is a British materials scientist and professor at the University of Cambridge. She is co-director of the Cambridge Centre for Medical Materials, where she studies materials that interact therapeutically with the body. Since October 2020 she has been joint head of the Department of Materials Science and Metallurgy at Cambridge.
Rachel Clare Thomson is a professor of Materials Science and Engineering, and Pro Vice Chancellor of Teaching at Loughborough University. She is known for her expertise in measuring and predicting the behaviour of materials for high temperature power generation, as well as the development of higher education and research programmes.
Light-emitting diodes (LEDs) produce light by the recombination of electrons and electron holes in a semiconductor, a process called "electroluminescence". The wavelength of the light produced depends on the energy band gap of the semiconductors used. Since these materials have a high index of refraction, design features of the devices such as special optical coatings and die shape are required to efficiently emit light. A LED is a long-lived light source, but certain mechanisms can cause slow loss of efficiency of the device or sudden failure. The wavelength of the light emitted is a function of the band gap of the semiconductor material used; materials such as gallium arsenide, and others, with various trace doping elements, are used to produce different colors of light. Another type of LED uses a quantum dot which can have its properties and wavelength adjusted by its size. Light-emitting diodes are widely used in indicator and display functions, and white LEDs are displacing other technologies for general illumination purposes.
Natalie Stingelin, Fellow of the Materials Research Society and Royal Society of Chemistry, is a materials scientist and current chair of the School of Materials Science and Engineering at the Georgia Institute of Technology, the University of Bordeaux and Imperial College. She led the European Commission Marie Curie INFORM network and is Editor-in-Chief of the Journal of Materials Chemistry C and Materials Advances.
Carol Trager-Cowan is a Scottish physicist who is a Reader in physics and Science Communicator at the University of Strathclyde. She works on scanning electron microscopy, including Electron backscatter diffraction (EBSD), diffraction contrast and cathodoluminescence imaging.
Allan Matthews (1952) is professor of surface engineering and tribology at the University of Manchester and director of the Digitalised Surfaces Manufacturing Network.
Martin D. Dawson is a British professor of photonics who is research director of the Institute of Photonics at the University of Strathclyde and is Head of Fraunhofer Centre for Applied Photonics. He has made pioneering contributions in several applied photonics areas.
Huili Grace Xing is the William L. Quackenbush Professor of Electrical and Computer Engineering, and Materials Science and Engineering in the Cornell University College of Engineering. In 2019, Xing was elected a Fellow of the American Physical Society (APS) "for pioneering contributions in polar wide-bandgap semiconductors, 2D crystal semiconductors and layered crystals," as well as Fellow of the American Association for the Advancement of Science (AAAS) in 2021.
The first Light-Emitting Diode (LED) was created in 1927 by Russian inventor Oleg Losev, and used silicon carbide as a semiconductor. However, electroluminescence as a phenomenon was discovered twenty years earlier by the English experimenter Henry Joseph Round of Marconi Labs, using the same crystal and a cat's-whisker detector. Despite having distributed his report in Soviet, German and British scientific journals, Losev's LED found no practical use for several decades, partly due to the very inefficient light-producing properties the semiconductor used.
