In a new headquarters in Linköping, Sweden, just down the road from the university, SweGan has reached a key milestone. Delivering 150mm (6in) wafers with its gallium nitride on silicon carbide (GaN-on-SiC) technology opens up high power, high frequency RF and power applications for chip makers.
GaN has been increasingly popular for chip designers with a layer of GaN on a silicon wafer but the current technology suffers from problems, says Jr-Tai 'Ted' Chen, chief technology officer and co-founder.
“In the power industry silicon has been the leading material for many years but now with high voltage devices people are convinced that wide bangap devices can do better,” said Chen. “In the market you can see SiC has a successful story. GaN fits in with medium power around 600 to 900V and the leaders in silicon have naturally moved to GaN on silicon as the substrates are cheap and that allows them to have vertical integration, so 99 percent of GaN devices are GaN-on-Si.”
“If you look at the quality of GaN on silicon there are still a lot of defects and the big question is reliability. This is where we can do a much better job with GaN on SiC – we use a different growth scheme. We have been developing this technology for ten years,” he said. “GaN on Silicon has to grow 5µm thick to get good quality but underneath you have the defects but a SiC layer is 2µm. Now for us it’s a 200 to 250nm layer as we can grow better quality with less defects.”
This thin epitaxial layer shows a much higher breakdown strength, four times higher than silicon. “It’s not the thickness, it’s about the quality,” he said. “In our structure we put the channel much closer to the SiC substrate and this helps to dissipate the heat."