IHS predicts silicon-based LEDs will nearly rival sapphire-based devices on market share come 2020. Compound Semiconductor finds out more.

Late last year, analyst business, IHS, forecast GaN-on-silicon LEDs will increase market share from today's 1 percent to an incredible 40 percent by 2020. This monumental 69 percent compound annual growth rate is at odds with other 2013 forecasts, but IHS analyst and author of 'GaN LEDs on Silicon - World - 2013", Dkins Cho, is certain the technology is poised for strong growth.

"In 2013, 95 percent of GaN LEDs were manufactured on sapphire wafers with only 1 percent manufactured on silicon," says Cho. "Come 2020, 40 percent will be manufactured on silicon, maybe 3 percent on SiC, with the remainder on sapphire substrates."

 
Forecasts of Market Penetration for GaN-on-silicon LEDs

According to Cho's forecast, the GaN-on-sapphire LED is still set to retain the largest market share, just. But given GaN-on-silicon's technical challenges, such as the lattice mismatch between GaN layers and the silicon wafer, as well as questionable manufacturing yields, is his forecast of near-market domination realistic?

Cho thinks so. As he points out, a few leading suppliers, most notably in Asia, have recently made good progress performance as well as throughput and yield on 6-inch to 8-inch wafers.

Declining to name companies he says: "Looking at the leading GaN-on-silicon LED companies, performance-wise, these manufacturers are producing devices with a similar performance to sapphire-based LEDs. Production yields are more of a problem, but some companies have already overcome this."

As Cho highlights, GaN-on-silicon LEDs have been successfully fabricated on 8-inch wafers using legacy CMOS fabrication facilities and equipment with just minor modifications. Indeed, many GaN-on-silicon LED heavyweights already own legacy 8-inch CMOS facilities, and could well be ready to migrate manufacturing to these fabs.

"Samsung and Toshiba already have CMOS semiconductor lines and have produced good devices," he says. "I also expect to see at least one Taiwan-based and two China-based companies enter the market."

The draw to silicon is largely ease of manufacturing and being able to use existing inspection tools. "Silicon has better machining characteristics than sapphire for laser cutting, grinding and polishing," says Cho. "CMOS fabrication on silicon has a long history of production using state-of-the art technologies so there is much greater process knowledge [than sapphire-based LED production]."

"And the process equipment is well developed and deployed over the entire front-end and back-end process," he adds. "GaN-on-silicon LEDs production can make use of legacy tools and facilities... to enhance process yields as well as overall yields and through-puts."

Legacy CMOS equipment can also be used for in-situ monitoring and inspection, potential leading to faster improvements in performance and has been achieved with sapphire-based LEDs to date. Still, Cho does not expect the likes of Toshiba and Samsung to convert to CMOS manufacturing immediately. "It is unlikely re-purposing will happen overnight," he says. "Instead we forecast a shift during the coming years."

CMOS rivals

While manufacturers of GaN-on-silicon LEDs will, without a doubt, chip away at the sapphire market share in coming years, other analysts do no concur with IHS's bold predictions. In the Summer of 2013, Lux Research analyst Pallavi Madakasira released her report "Dimming the Hype: GaN-on-silicon Fails to Outshine Sapphire by 2020".

As she asked Compound Semiconductor at the time: "Can we really expect an organisation that has invested billions of dollars in its GaN-on-sapphire line to stop running that?" Questioning the performance of GaN-on-silicon LEDs, she also stated: "You have to remember that [GaN-on-silicon LED manufacturers] are catching up on a moving target. GaN-on-sapphire performances will keep improving and costs are going to keep coming down."

And then there's the added complication of Cree. With its continued investment in SiC production and successful transition from 4-inch to 6-inch diameter wafers, can industry really expect the US-based industry heavyweight to lose out to silicon rivals in such a big way?

Still, Cho is standing by his forecasts. Cheap fabrication costs aside, he believes a rising demand for LEDs for medium power lighting as well as applications such as LED-backlit LCD displays will boost GaN-on-silicon LED manufacturing.

He also highlights how he has analysed the manufacturing cost and price behaviour of major suppliers across the supply chain as well as interviewed GaN-on-silicon developers and companies not moving to GaN-on-silicon technology.

"The companies already making GaN-on-silicon LEDs have sold out production," he says. "Sapphire and silicon carbide market share will continue to go to silicon."