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LEDs: Big lights come in small packages

Posted: 02 Jun 2014 ?? ?Print Version ?Bookmark and Share

Keywords:LEDs? GaN-on-Si? sapphire? silicon?

Light-emitting diodes (LEDs) were first commercially used in the 1960s as replacements for neon and incandescent lamps found in expensive laboratory and electronic test equipment. The cost of infrared and visible LEDs units was so steep back then that there was limited practical use. These days, the technology has found its way in diverse applications ranging from consumer electronics to industrial, automotive headlamps, traffic signals, billboards and aviation lighting.

Sapphire vs silicon

The use of LEDs in lighting applications has soared over the past decade because of advantages such as longer lifetime and lower energy consumption compared to incandescent light sources. However, manufacturing costs continue to hamper its uptake. Gallium nitride (GaN) on sapphire substrate technology, developed in the early 1990s and provided the foundation for high-brightness blue LEDs, is currently the most commonly used production process. Gallium nitride on silicon (GaN-on-Si) is now emerging as a less costly alternative to sapphire.

A major setback in utilising silicon as a substrate is the misalignment of its atoms to those in a GaN layer. This would cause strain that can be remedied through sporadic dislocations, which would lead to leakage currents. To avoid this problem, a buffer layer is used to match the silicon lattice before transposing it into GaN.

Market research firm Yole Dveloppement points out that although GaN-on-Si offers significant cost benefits for LEDs, mass adoption remains uncertain. Major LED manufacturers are involved in GaN-on-Si LED research yet only a handful have incorporated the technology in their roadmaps. The only LED products manufactured via GaN-on-Si available in the market so far are from Plessey Semiconductors, Lattice Power and Toshiba.

LED-based lighting

LED products are thriving as energy-efficient alternatives for commercial and industrial lighting applications. Global revenue for packaged LEDs is expected to hit $7.1 billion by 2016, up 96 per cent from $3.6 billion in 2013, according to IHS. Asia is a major player in this market, accounting for about 70 per cent of packaged LEDs shipped worldwide in 2012 and 2013, IHS market analyst Stewart Shinkwin told EE Times Asia. Strategies Unlimited predicts a unit growth of 30 per cent for LED replacement lamps to reach $3.7 billion in the next two years. LED replacements for linear fluorescent lamps yield highest units sales numbers in China and Japan. In most Asia Pacific markets, governments are committing large amounts of funding to basic infrastructure, creating a wide range of business opportunities, according to a report from Navigant Research.

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