24 June 2022
New state-of-the-art results have been reported for high-voltage GaN power devices enabled by the MIS-HEMT technology of Chalmers University of Technology in Gothenburg, Sweden and the QuanFINE buffer-free gallium nitride on silicon carbide (GaN-on -SiC) materials of Linköping-based epitaxial wafer foundry SweGaN AB (Björn Hult et al, ‘High Voltage and Low Leakage GaN-on-SiC MISHEMTs on a “Buffer-Free” Heterostructure’, IEEE Electron Device Letters, volume 43, issue 5 (May 2022), p781).
Among key findings, the research identifies QuanFINE epiwafers as a highly competitive candidate for high-voltage power devices in 1200V applications, in addition to its strong traction in the RF market at present.
Picture: Specific on-resistance versus breakdown voltage benchmark using the 1µA/mm current criterion.
Existing GaN power devices available on the market have been limited to a rating of 650V, due to their GaN material quality and low-breakdown silicon substrates. However, by fabricating GaN power devices on buffer-free GaN-on-SiC materials with total epilayer thickness roughly 20 times thinner than that of commercial GaN-on-Si epiwafers (see Figure 1), high-voltage operation with exceptionally low gate and drain leakage currents has now been demonstrated. Specific on-resistance of 3.61mΩ.cm2 and an off-state breakdown voltage of 1622V at a drain current of 22nA/mm have been achieved, as well as a vertical breakdown voltage of more than 3000V (see Figure 2).
Picture: Off-state breakdown characteristics at Vgs = -20V of a MISHEMT with Lgd = 20µm. (b) Breakdown voltage of MISHEMTs and two-terminal isolation structures with varying Lgd and L.
The results are reckoned to demonstrate the significant potential of SweGaN’s QuanFINE epitaxial solutions for high-voltage GaN power devices in applications where the performance and reliability of the devices are both strictly required, eg in on-board chargers and power inverters in electric vehicles (EVs ).
“With excellent results establishing the robust capability of our material, we anticipate there will be growing opportunities for SweGaN in this era of electric vehicles, where the power devices are critical for the vehicle’s performance,” says SweGaN’s chief technology officer Dr Jr-Tai Chen . “We are currently in discussions with early-adopter GaN power device companies to launch high-voltage power solutions that harvest the true advantages of GaN,” he adds.
“SweGaN has developed highly robust and innovative GaN-on-SiC materials,” comments Chalmers professor Niklas Rorsman. “We are happy to collaborate with SweGaN on a continuous basis to perform joint research and development,” he adds.
“The collaboration of Chalmers and SweGaN have been successful on numerous research projects,” notes SweGaN’s CEO Jonas Nilsson. “Harnessing the combined expertise from the material level to the device level is the key behind this achievement, which will also further enhance SweGaN’s long -term market strategy and product innovation – and provide significant benefits to our global customer base.”
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