Boffins create single-electron transistors

Scientists have demonstrated the first reproducible and controllable silicon transistors that are turned on and off by the motion of individual electrons.

The experimental devices, designed and fabricated at NTT Corp in Japan and tested at the US National Institute of Standards and Technology, could have applications in low-power nano-electronics, particularly as next-generation integrated circuits for logic operations.

The transistors, described in the 30 January issue of Applied Physics Letters, are based on the principle that as device sizes shrink to the nanometre range, the amount of energy required to move a single electron increases significantly.

This phenomenon makes it possible to control individual electron motion and current flow by manipulating the voltage applied to barriers, or 'gates', in the electrical circuit.

"At negative voltage, the transistor is off; at higher voltage, the transistor is turned on and individual electrons file through the circuit, as opposed to thousands at a time in a conventional device," the scientists explained.

"This type of innovative transistor, called a 'single-electron tunneling' device, is typically made with a metal 'wire' interrupted by insulating barriers that offer a rigid, narrow range of control over electron flow.

"Silicon devices, by contrast, have barriers that are electrically 'tunable' over a wider operating range, offering finer, more flexible control of the transistor's on/off switch."

The team made five uniform working silicon transistors with tunable barriers. Each device consists of a 360 x 30 nanometre silicon channel with three gates crossing the channel.