Discovery could improve reliability of future smart electronics

Hot-carrier effects occur when unwanted electron energy builds up in certain regions of transistors, resulting in devices performing unreliably.

In her final-year project, Lea Motte studied a new device, the multimodal transistor, an alternative to conventional thin-film transistors, invented and developed by PhD candidate Eva Bestelink and supervisor Dr Radu Sporea at Surrey.

Lea used a defining feature of multimodal transistors, the separation of controls for introducing electrons into the device and allowing them to move across the transistor. Through computer simulations, Lea discovered that choosing the right voltage to apply to the transport control region can prevent unwanted hot-carrier effects. In addition, it ensures that the current through the transistor remains constant in a wide range of operating conditions.

In a paper published in the journal Advanced Electronic Materials, PhD student Eva Bestelink systematically studies Lea's discovery of the unusual behaviour in multimodal transistors by confirming it with measurements in microcrystalline silicon transistors and performing extensive device simulations to understand the device physics that underpins its unique ability.

This discovery means that future technologies that use multimodal transistors could be more power-efficient, and it could lead to high-performance amplifiers, which are essential for measuring signals from environmental and biological sensors.

Eva Bestelink, lead author of the study from the University of Surrey, said:

"We now have a better understanding of what the multimodal transistor can offer when made with materials that cause numerous challenges to regular devices.

"For circuit designers, this work offers insight into how to operate the device for optimum performance. In the long term, the multimodal transistor offers an alternative for emerging high-performance materials, where traditional solutions are no longer applicable."