European researchers have developed a hybrid GaN-on-SiC wafer technology that builds gallium nitride on a silicon carbide substrate for higher performance power devices.
SweGaN in Linköping, Sweden, worked with Linköping University and IEMN in France on the technique, called Transmorphic Heteroepitaxy. This grows an atomic ‘interlayer’ less than 1nm thick with ordered vacancies to accommodate the lattice mismatch between the two materials.
This new growth mechanism suppresses the formation of structural defects in the beginning of the epitaxy, which enables grain-boundary-free nucleation layers and allows high performance GaN-based structures to be built. A GaN HEMT heterostructure with a total thickness less than 300 nm grown by the transmorphic epitaxial scheme on a semi-insulating SiC substrate shows a lateral critical breakdown field of ~2 MV/cm and a vertical breakdown voltage of ≥ 3 kV, measured by the senior researchers at IEMN.
This is nearly 3 times higher than that of GaN-on-Si epiwafers grown by the conventional thick-buffer approach. This means that the ON-resistance of devices built on the epiwafers can be ten times lower.
SweGaN collaborated with the scientists in electron microscopy and modeling from Linköping University and IEMN on the material, called QuanFINE.
“Not only is this a high-impact innovation, but comes together with a scientific discovery of a novel epitaxial growth mechanism, what we coin transmorphic,” said Lars Hultman, professor at Linköping University and member of the Royal Swedish Academy of Sciences.
“This breakthrough could significantly reduce the power loss for high power devices, which would truly manifest the superiority of GaN power devices over Si super-junction power devices and SiC MOSFETs for 650V rated devices,” says Jr-Tai Chen, CTO at SweGaN.
“With these new results, SweGaN will now extend the focus of its QuanFINE technology to include the global power market in addition to RF devices for satellite, communications and defence organizations, particularly in Asia showing the most hunger for new generation GaN power devices,” said Chen.