Zero-micropipe wafers prompt SiC Schottky ramp
SiC chip manufacturer Cree says that it is now shipping a high-power SiC Schottky rectifier that improves transmission efficiency across an electrical grid.
Rated at 50 A and 1200 V, the rectifier can be used in so-called inverter modules that convert the direct-current electricity generated by renewable sources such as wind turbines and solar cells into an alternating current.
These inverters traditionally use silicon-based diodes, which operate at between 90 percent and 96 percent efficiency. However, Cree sys that this can be improved to up to 98 percent by using SiC-based devices instead.
If deployed widely over a power network, that slightly better performance could potentially slash overall electricity transmission losses, creating a far more energy-efficient grid (see related magazine feature article).
Motor drives and electric vehicles could also benefit from the SiC-based rectifiers, which have the added benefits of eliminating the need for "snubber" components, enabling cooler operating temperatures (because of their higher efficiency), and producing less electromagnetic interference than a silicon equivalent.
Cree has been working with the major Japanese utility company Kansai Electric Power for nine years on applications of SiC inverters, and Kansai is hoping to use SiC-based inverters to connect wind turbines to the grid network in Japan.
"Tremendous energy savings could be realized by switching from silicon to SiC inverters," said Yoshitaka Sugawara, Kansai s SiC program manager.
Thanks to recent advances in SiC material quality, the new rectifiers can deal with higher power levels than any products previously released by Cree.
At 8.2mm x 4mm, the die-size is the largest in the SiC industry, and it is this property that lends the component its ability to handle very high powers. But such large die can only be used if the underlying SiC material is of very high quality so that micropipe defects do not impact device performance.
John Palmour, Cree s executive VP for advanced devices, says that the large-die rectifier is a direct result of material quality improvements made within the past year: "Fundamental to these advances are very low defect density substrates, including zero-micropipe SiC substrates," Palmour said.
Cree gained this zero-micropipe technology through its acquisition of Intrinsic Semiconductor in summer 2006 in a mostly-cash $46 million deal (see related story).
