SweGaN, IEMN and Linköping University unveil Transmorphic Heteroepitaxy GaN-on-SiC growth process for power devices

A project funded by the European Union’s Horizon 2020 research and innovation program has contributed to custom gallium nitride on silicon carbide (GaN-on-SiC) epitaxial wafer manufacturer SweGaN AB of Linköping, Sweden collaborating with Linköping University and IEMN (a French research group dedicated to high-power devices) to develop the new epitaxial growth mechanism Transmorphic Heteroepitaxy for producing next-generation GaN-on-SiC power devices (‘Transmorphic Epitaxial Growth of AlN Nucleation Layers on SiC Substrates for High-Breakdown Thin GaN Transistors’, Applied Physics Letters, vol115, no22, 25 November 2019).

Specifically, SweGaN collaborated with the scientists in electron microscopy and modeling at Linköping University and senior researchers at IEMN to explore the nature of the new epitaxial growth mechanism and the potential of SweGaN’s QuanFINE hybrid GaN–SiC heterostructures for high-power device applications (joining to the firm’s existing product portfolio for RF components and devices).

“Not only is this a high-impact innovation, but it comes together with a scientific discovery of a novel epitaxial growth mechanism, which we coin transmorphic,” says the paper’s co-author 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 silicon super-junction power devices and silicon carbide MOSFETs for 650V-rated devices,” says chief technology officer Jr-Tai Chen.

The new results show Transmorphic Heteroepitaxy growth where less than 1nm-thick atomic interlayers with ordered vacancies are created to sufficiently accommodate the lattice mismatch at the interface between the first epilayer and the substrate.

SweGaN highlights the following features:

The new growth mechanism suppresses the formation of structural defects in the beginning of the epitaxy, which enables grain-boundary-free aluminium nitride (AlN) nucleation layers and subsequent high-quality buffer-free GaN-based heterostructures to be realized on SiC substrates.
A GaN high-electron-mobility transistor (HEMT) heterostructure with a total thickness of less than 300nm grown by the transmorphic epitaxial scheme on a semi-insulating SiC substrate shows a lateral critical breakdown field of ~2MV/cm and a vertical breakdown voltage of ≥3kV (measured by senior researchers at IEMN).
The critical breakdown field is nearly three times higher than that of GaN-on-Si epiwafers grown by the conventional thick-buffer approach. So, the device’s ON-resistance has the potential to be lower by more than one order of magnitude than the value achievable currently, according to Baliga’s figure of merit (BFOM).

“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, particularly in Asia showing the most hunger for new-generation GaN power devices,” says Chen. “We anticipate releasing more new findings on the performance of QuanFINE based power devices in the near future.”

See related items:

Thin gallium nitride on silicon carbide high-power and high-frequency electronics

Nitride epiwafer firm SweGaN raises $750,000 in new share issue

Tags: GaN-on-SiC HEMT MOCVD Epitaxial wafers

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