The popular theory for reconciling the excellent emission efficiency of GaN LEDs with their very high defect density is based on evidence of clustering in the InGaN quantum wells. But recent atom probe measurements have disproved this idea by showing that InGaN actually forms a random alloy, according to Mark Galtrey, Rachel Oliver, and Colin Humphreys from Cambridge University.
Installed as vice-president of TriQuint's handset business unit in July 2006, Tim Dunn has already overseen a rapid upturn in the maker's wafer volumes and product sales. Dunn was understandably in a chirpy mood when he met Michael Hatcher at the 3GSM World Congress in Barcelona, Spain.
Germanium substrates are an unlikely candidate for nitride growth. However, a unique meshing ratio actually enables the fabrication of high-quality GaN directly on this platform, says IMEC's Ruben Lieten. The development could ultimately lead to more efficient and powerful HBTs.
Switching from a buried ridge-waveguide structure to an inner stripe design can increase the output power of single mode lasers to a record-breaking 1000 mW, says NEC. Richard Stevenson investigates the novel approach.
A partnership between Ukraine, Russia, Greece and the US has developed a series of SiC PIN diodes for microwave applications. The devices already deliver a better performance than incumbent silicon and GaAs equivalents, says team member Nicolas Camara, and more improvements are expected.
Although epiwafer foundry IQE is returning to financial health, the UK's two biggest compound semiconductor chip facilities are still struggling to make ends meet. Michael Hatcher evaluates their performance.
Representing only a small niche in the market for large LCD displays, sales of LED-based backlight units will nevertheless grow rapidly between now and 2009. But the likely value of this emerging sector for LED manufacturers is a tough one to call. Michael Hatcher reviews the forecasts.
Philips Lumileds has combined its thin-film structure with a flip-chip design. The result, say Oleg Shchekin and Decai Sun, is a highly efficient device for lighting applications that delivers a better performance than vertically injected LEDs.
Richard Stevenson quizzes Sudhakar Raman, Veeco's vice-president of marketing for MOCVD operations, about the introduction of the company's K300 and K465 "future-proof" reactors for GaN LED production.
Finally, tunable lasers are the way they are meant to be – smaller, faster, power-efficient and reliable, says Syntune's Kevin Green. This is accomplished with designs based on conventional lasers, an approach that has produced the first monolithic 10 Gbit/s tunable transmitter for optical networks.
France's Alcatel-Thales III-V Lab has built InAs quantum-dash lasers on InP substrates that share the attributes of quantum-dot lasers, but are easier to fabricate. Béatrice Dagens, François Lelarge, Alain Accard and Guang-Hua Duan explain their use in next-generation optical networks.
Many MMIC and RFIC designers are still using primitive modeling techniques that ignore image noise and non-linear effects. Because these omissions can postpone product launches and hit sales, argues Chris Paris, designers should use dedicated software that can expose circuits' weaknesses.
Jerry Zimmer, Gerry Chandler and Dwain Aidala from sp3 Diamond Technologies describe how silicon-on-diamond substrates are able to reduce the cost of GaN HEMTs and improve their reliability and output power.
A widespread move among manufacturers of LEDs to prepare for the next big wave of applications means that the order books of Veeco Instruments and Aixtron are bulging, and prospects look set to improve.
Quizzing the Air Force Research Laboratory's Laura Rea about the US military's technology roadmap, Bob Metzger hears how a dramatic shift in strategic thinking will affect the role of compound semiconductors.
If we are going to harness the true extent of the Sun's energy, multi-junction solar cells are one option. But as Jon Cartwright reports, we could do it with multi-band cells – a new technology that RSL Energy promises will deliver the power conversion efficiency of triple-junction GaAs-based photovoltaics at the same price as single-junction devices.
Ineffective current blocking layers cause an efficacy drop in LEDs at high drive currents, say Ioffe Institute researchers Igor Rozhansky and Dmitry Zakheim. They believe that this can be overcome by switching to an n-p-n structure, as Richard Stevenson reports.
Oliver Ambacher and Gabriel Kittler from the Technical University of Ilmenau describe how a European consortium is building a medical analysis tool from GaN devices for use in hospitals and laboratories.