These devices are promising candidates to replace MOSFET transistors in future chip generations for ultralow-power applications operating on ultralow supply voltages. [ The illustration shows a scanning electron microscope image of a typical TFET in a verical configuration and is from the imec magazine .]
TFETs exploit a different mechanism to inject carriers than MOSFETs, the most dominant transistor type today. While MOSFETs introduce carriers from the source into the conducting channel by thermal injection, a TFET works through band-to-band tunneling (BTBT). With that, they promise sub-threshold swings smaller than 60 mV/dec, which is below the limit of what is possible with MOSFETs. This would allow operating them at ultralow supply voltages (below 0.5V).
The device developed at imec is an InGaAs homojunction TFET. It shows a minimum sub-threshold swing of 54 mV/dec at 100 pA/mm. The sub-threshold swing remains sub-60 mV/dec over 1.5 orders of magnitude of current at room temperature. The EOT of the devices is 0.8 nm, which plays a major role in achieving the desired sub-60 mV/dec performance.
“We have entered an era where new chip technologies require making trade-offs between power, performance, cost and area. And these trade-offs will be considered separately for different application domains,” says Nadine Collaert, distinguished member of technical staff at imec. “TFETs will most probably find their place in the ultralow-power segment. Many applications in the future require transistors to work at low power and low voltage, such as the many Internet of Things applications.
At the conference, imec’s expert Nadine Collaert will discuss the progress made and challenges ahead in processing TFETs, focusing on the materials and integration, but also on the impact of using TFETs in electronic circuits.
** CS International Conference (Brussels, March 7-8, 2017)