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Diamond transistor with high on voltage

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January 30, 2025

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A team of international researchers has found a new way to use diamond as the basis of a power transistor that remains switched off by default.

The 1µm transistor developed at the University of Glasgow in the UK switches at 6V and can carry more current than other designs.

Diamond as a wide bandgap material like silicon carbide is also a better thermal substrate, allowing more current to flow. This design uses a coating of hydrogen atoms followed by layers of aluminium oxide.

The team used an Accumulation Channel rather than a Transfer Doping regime to improve how efficiently charge moves through the device, achieving twice the performance compared to traditional diamond transistors. In practical terms, this means electrical charge can move more freely through the device, improving its efficiency and giving a current density of over 80mA/mm2 and gate leakage of less than 40nA/mm2.

“The challenge for power electronics is that the design of the switch needs to be capable of staying firmly switched off when it’s not in use to ensure it meets safety standards, but it must also deliver very high power when turned on,” said Professor David Moran, of the University of Glasgow’s James Watt School of Engineering, led the research team with partners from RMIT University in Australia and Princeton University in the US.

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“Previous state-of the-art diamond transistors have generally been good at one at the expense of the other – switches which were good at staying off but not so good at providing current on demand, or vice-versa. What we’ve been able to do is engineer a diamond transistor which is good at both, which is a significant development.”

When switched off, the device’s resistance is high enough that it measured below the noise floor of the team’s equipment in the lab meaning almost zero current leaks through when it’s supposed to be off, a crucial safety feature for high-power applications.

“These are really encouraging results, which bring diamond transistors much closer to achieving their potential than ever before,” said Moran. “The production cost for diamond is surprisingly low for a material that many people associate with luxury goods, but there are still challenges to be addressed before diamond transistors are ready to be scaled up by the manufacturing industry. We hope that our research will help drive forward the adoption of diamond transistors across industries in the years to come.”

Extreme Enhancement-Mode Operation Accumulation Channel Hydrogen-Terminated Diamond FETs with Vth <−6V and High on-Current’

 

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