NEWS ANALYSIS


Sapphire substrates


to lead future LED markets Come 2020, US analyst business, Lux Research, predicts sapphire- based LEDs will still dominate a multi-billion dollar LED lighting industry. Compound Semiconductor finds out why.


LED LIGHTING is forecast to become a $80 billion industry by the end of the decade, with manufacturers of LEDs based on sapphire, silicon and silicon carbide substrates jostling for market space. Today, the vast majority of devices are deposited on sapphire wafers, but could this change?


Both Plessey Semiconductors and Toshiba-Bridgelux recently unveiled GaN-on-silicon LEDs and have promised mass production before the end of this year while Cree is relentless in its delivery of GaN-on-SiC devices. But despite the progress, Lux Research analyst, Pallavi Madakasira, is certain GaN-on-sapphire LEDs will remain the industry’s leading lights.


In her recent report, Dimming the Hype: GaN-on-silicon Fails to Outshine Sapphire by 2020, she predicts GaN- on-sapphire will remain the entrenched incumbent come the end of the decade. Meanwhile, the leading emerging technology, GaN-on-silicon, will snare only 10 percent market share while GaN-on-SiC will grow to 18 percent of the market. This, she believes, is down to cost and performance.


“GaN-on-silicon developers tout very loudly that fully 22 www.compoundsemiconductor.net August / September 2013


depreciated [CMOS] equipment can be used to make GaN-on-silicon [devices],” she says. “But can we really expect an organisation that has invested billions of dollars in its GaN-on-sapphire line for more than ten years to stop running that, and get into GaN-on-silicon [production].”


As she points out, industry players know how to make silicon substrates ‘with their eyes closed’, but depositing complex buffer layers onto silicon prior to GaN deposition, to overcome GaN and silicon lattice mismatches, adds time and cost to a manufacturing line.


“As much as these lines are full depreciated, they are still an additional investment for a company space- and time- wise,” she says. “It’s common knowledge that almost all the big businesses, such as Philips and Osram, have in- house programmes looking at GaN-on-silicon... but it’s very unlikely you will see, say, Philips quit its GaN-on-sapphire programme and then move into GaN-on-silicon,” she adds.


Madakasira also highlights that the performance of GaN- on-silicon LEDs has yet to be favourably demonstrated compared to alternative technologies. Her figures put the luminance efficacy of GaN-on-SiC LEDs at 200 lumens per


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