UK team leads diamond-FET breakthrough
A landmark development led by researchers from the University of Glasgow could help create a new generation of diamond-based transistors for use in high-power electronics.
The team have found a new way to use diamond as the basis of a transistor that remains switched off by default - a development crucial for ensuring safety in devices which carry a large amount of electrical current when switched on.
Diamond has an inherently wide band gap, making it is capable of handling much higher voltages than silicon before electrically breaking down, making it particularly attractive for high power electronic applications like power grids or electric vehicles.
David Moran, a professor at 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 USA. Their research 'Extreme Enhancement-Mode Operation Accumulation Channel Hydrogen-Terminated Diamond FETs with Vth <−6V and High on-Current’, is published in the journal Advanced Electronic Materials.
Moran said: “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.
“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.”
At the University of Glasgow’s James Watt Nanofabrication Centre, the team used surface chemistry techniques to improve the performance of diamond, coating it in hydrogen atoms followed by layers of aluminium oxide.
Their diamond transistor requires six volts to switch on, more than twice the voltage compared to previous diamond transistors, while still delivering high current when activated.
They also improved 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.
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.
Moran added: “These are really encouraging results, which bring diamond transistors much closer to achieving their potential than ever before. 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.”
Pictured above: a) Accumulation Channel H-diamond FET structure concept and associated representative energy band diagram in contrast with b) a 'typical' Transfer-Doped H-Diamond FET.
