NEWS ANALYSIS
IN JULY THIS YEAR, Australia-based semiconductor process developer, BluGlass, won Aus$3 million in federal government funding to demonstrate high efficiency, low cost GaN LEDs.
The start-up has spent years honing the low temperature growth of GaN, and more recently the growth of p-GaN layers, on MOCVD GaN templates but will now ramp up efforts to grow entire LED structures on silicon substrates as well as sapphire wafers.
“Our lower temperature remote plasma CVD has the potential to reduce the bowing and cracking problems of traditional high-temperature MOCVD... and we can see emerging opportunities in GaN-on-silicon markets,”explains company chief technology officer, Ian Mann.
To achieve low temperature growth, BluGlass replaces the ammonia source of a typical MOCVD system with nitrogen gas, passed through an electrical coil to generate a plasma. During conventional MOCVD, temperatures of up to 1200 °C dissociate nitrogen from ammonia, and GaN layers are grown. But by directly supplying nitrogen via a plasma, BluGlass deposits the semiconductor layers at much lower temperatures.
To date, the company has not revealed actual growth temperatures but earlier this year it showcased p-GaN films, grown via RPCVD on MOCVD GaN templates, that met industry electrical performance benchmarks. Mann claims the process is cheaper than MOCVD as large amounts of ammonia are not used, although a RPCVD deposition tool will cost about the same as an
BluGlass raises LED ambitions
Following federal funds, BluGlass is eyeing GaN on silicon LED markets.
MOCVD system. His team is now working towards growing p-GaN layers at low temperatures and aims to grow at temperatures matching those used in MOCVD growth of multi-quantum wells.
“Today we buy multi-quantum well layers made on an MOCVD machine and we grow p-GaN layers on top of these,” says Mann. “But with our technology, some of the real value will come from growing the multi-quantum wells and then the p-type GaN layers at the same temperature all via RPCVD. We believe this is achievable. And crucially, as Mann highlights: “A low temperature p-GaN layer has the potential to be less damaging to the MQW and therefore improve the efficiency of an LED.”
The recent funding has enabled the firm to buy a second, larger MOCVD system, that Mann and colleagues will now retrofit to a RPCVD system. The CTO emphasises that the system will be smaller than the size of a production facility in a tier one fab, but will allow the team to work with single, 8-inch wafers.
“The system will allow us to demonstrate 8-inch silicon, which is a must-have and isn’t something we can do with our current development equipment,” he says. The team is currently developing nucleation and multi-quantum well layers, and while the RPCVD process will differ from conventional MOCVD, Mann asserts: “We will use RPCVD to grow a full structure in the same way that MOCVD can grow a full structure.”
“At the same time we are also looking to commercialise as fast as we can and will draw on other resources, potential partnerships and other funding to accelerate this,” he adds.
But what of the company’s starting technology – blue light emission from GaN deposited on glass?
According to Mann, BluGlass is now focused on the conventional substrates that the LED industry is familiar with. And the company doesn’t expect to stop at LEDs, but intends to take its technology to power electronics markets.
BluGlass now hopes to take its remote plasma CVD process to LED and power electronics markets. [Credit: BluGlass]
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www.compoundsemiconductor.net October 2013
“Clearly the power electronics market is an emerging market as well,” highlights Mann. “And from a technology point of view, getting good quality GaN growth on silicon is important for both power electronics devices and LEDs.”
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