GaN-on-Si LEDs catching up with incumbents

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Toshiba has announced a second generation of GaN-on-silicon lighting LEDs.Fabricated on 200mm silicon wafers, "luminous efficacy of the TL1F2 white LEDs has been improved compared with the TL1F1 series by optimising the package and increasing the optical output power of the GaN-on-Si LED chips", said the firm. "The TL1F2 series offers a colour temperature range from 2,700 to 6500K, with minimum colour rendering index [CRI] values of 80 and 70 respectively. Typical luminous flux of the 1W LEDs ranges from 104 to 135 lm depending on colour temperature and CRI."These GaN-on-Si lm/W figures are now similar to those from LEDs made with more traditional methods, providing they have been measured 'hot' – at say 85C.Despite its complex epitaxy, which has taken so long to develop, GaN-on-Si is expected to result in cheaper LEDs compared with those made on sapphire and SiC because the substrate is cheaper and can be larger. The Toshiba devices are supplied in a standard 6450 package measuring 6.4×5.0×1.35mm.Typical driving current is 350mA, with a typical forward voltage of 2.85V - lower than most '1W' LEDs.Operating range is -40 to 100°C, and applications are expected indoors in lamps and ceilings, and outside in street lamps and floodlights, said Toshiba.Mass production of the TL1F2 series is scheduled for November 2013. Luxeon UVPhilips Lumileds a family of high flux density LEDs in wavelengths of 380-430nm.The Luxeon UV LEDs are designed for applications including ultraviolet curing, counterfeit detection, medical, industrial and specialty lighting."The UV LED market has been hampered by limited flux density and a lack of design flexibility," said Kurosh Hashemi, Senior Product Line Manager at Philips Lumileds."The company addressed these limitations by introducing a compact, high-power emitter that can be tightly spaced to deliver the highest flux density to the desired medium. For example, for curing applications, 395nm emitters enable arrays of up to 38W/cm2 when driven at 1A," said Hashemi.The device micro-footprint is 2.2mm2, and each LED is provided in undomed form for precise optical control.The UV LEDS are designed to accept 1A drive currents. The package uses flip chip assembly, where the chip is in direct contact with the thermally conductive AlN substrate.

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