
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. Their new diamond transistor overcomes the limitations of previous developments in the technology to create a device much closer to being of practical use across a range of industries which rely on high power systems.
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 that carry large currents when turned on.
Diamond has an inherent property known as ‘wide band gap’, meaning that it is capable of handling much higher voltages than silicon before electrically breaking down. In power electronic applications, that means that transistors made from materials such as diamond can withstand significantly higher voltages and deliver higher power than the standard Si transistors.
The team’s diamond transistor could also find applications in sectors where large voltages are required and efficiency is highly-valued, such as power grids or electric vehicles.
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 USA. Their research is published as a paper in the journal Advanced Electronic Materials.
The power challenge
Prof 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.
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 exhibits almost zero current when it is turned off, a crucial safety feature for high-power applications.
Prof 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 … 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.”
The team’s paper, titled ‘Extreme Enhancement–mode Operation Accumulation Channel Hydrogen–terminated Diamond FETs with Vth < –6V and High On-current’, is published in Advanced Electronic Materials.