Alan Mills

Lighting: The progress & promise of LEDs

Abstract Advances in light output power from LED sources continue, with one of the latest markers being the development of a 1200 lumen white LED lamp by Cree. (It would be equivalent to a 75W incandescent bulb.) Although it is still a long way from commercial availability, it is one of the latest milestones towards developing general lighting products from solid state light sources.

First time III-nitride photonic crystals

Abstract The development of compound semiconductor photonic crystals (PCs) based on infrared devices (wavelengths longer than 700nm) has been quite rapid during the last few years, mostly focused on Indium Phosphide materials for optical communication uses in the 1.3 and 1.55nm transmission windows. The property being exploited is the ability of lattices of varying refractive index to form photonic bandgaps in which the propagation of specific light wavelengths is prohibited or modified. This property can be used to control or enhance the spontaneous emission and or light extraction efficiencies from both active and passive devices (including LEDs).

Strategies in Light 2006: record LED sales but price erosion

One of the first meetings to brighten up the annual LED calendar year has traditionally been the Strategies in Light Conference (SIL). This years meeting in San Francisco, hosted by the Strategies Unlimited division of PennWell, was no exception. SIL 2006, the 7th in this longest running and pace-setting LED Industry series, can claim a record attendance of almost 500 delegates perhaps logically supported by record sales volumes of high brightness and ultra-high brightness LEDs.

Advances in LED packaging

The ever-growing market for packaged LED lamps is constantly demanding easier ways to incorporate brighter and more powerful LED sources. This demand comes at a time when compound semiconductor packaging may now be as, or more, important than the LED chip production process itself, as higher and higher package performance is required. And, package selection in the USA recently increased as Cotco International Ltd entered the market with a new family of high output white (and coloured) LED packages.

Phosphors to brighten your future

As the efficiency of electric lighting has improved over the last 150 years it has progressed from carbon, tantalum, osmium and tungsten filaments through gas discharge lamps (mercury, neon, xenon), and now in the 21st century solid-state lighting will have the impetus for the foreseeable future. Even though fluorescent lamps have now achieved 100 lumens per watt, this value was recently matched by a low-power, phosphor-coated blue LED.

Phosphors development for LED lighting

The use of phosphors by man probably started more than 2000 years ago when they were used in fireworks to modify the colour output, but real phosphor development is a 20th century phenomena starting in the 1940s, and its more recent development has most of the market demand being generated by cathode ray tubes (TVs, PC monitors, test equipment) and fluorescent lighting. However, during the last five years white LEDs have become very important lighting sources and the importance of LED phosphors for white and coloured light generation must be considered an important market driver in the future, and perhaps unfortunately, as a disruptive technology.

Bristol University and Quantum Focus set to revolutionise thermal imaging

A few years ago, we reported on the benefits of a micro-Raman analytical technique to determe the temperature of active, GaN-based, III-V devices developed by Martin Kuball et al at UKs University of Bristol. This method uses the phonon frequency dependency with temperature in micro-Raman spectra, to measure the temperature of sub-micron regions of an operating device, such as a FET or HEMT gate region. Where these regions are accessible to microscopic examination, micro-Raman spectra allow the device surface temperature to be estimated to within about five °C. The excitation source is a one-micron laser spot from a 488nm argon laser (3mW power). It provides insignificant heating of the device chips, which are transparent at this wavelength.

Trends in HB-LED markets

Abstract Strategies Unlimiteds Strategies in Light 2001 conference in San Francisco in February highlighted the major trends and growth prospects of the various sectors of the light emitting diode market, particularly for AlGaAs red, AllnGaP red, yellow and green, and InGaN green, blue and white High-Brightness LEDs.

Wide-bandgap emitters continue to improve

Abstract The Fall-99 MRS meeting opened in Boston following the traditional Thanksgiving Weekend holiday. But, for those really dedicated to the subject matter, the meeting started on the Sunday with a popular tutorial on III-nitrides (with more that 100 in attendance), given by Shur and Schowalter from Rensselaer Polytechnic Institute. These attendees were provided with a comprehensive and entertaining dialogue on III-nitride materials, with enough background information to propel them into the forefront of wide-bandgap development technology early in the new millenium.

Eurotour' 96 — The wide bandgap special Rigi-Strasbourg-Cardiff

Abstract In June of this year the GaN scientific community had a unique opportunity; three continuous conferences with European locations all loaded with GaN content. Combined they provided an unguided European tour that included a taste of Switzerland, France and Wales and the opportunities to use ancient and modern transportation technology — an antique paddle streamer, a rack railway and the Channel Tunnel. Modern trains may use SiC power control devices, were any GaN emitters used for the Chunnel signaling?