At IMEC's Holst Center in Eindhoven, The Netherlands, researchers are looking to produce transistors designed to operate at 0.2 or 0.3 volts at the sub-threshold region. The key to pursuing such ultra-low power goals: silicon.

Researchers are also looking at sub-threshold operation. "We are doing some work to characterize silicon. The issues around transistor operation are completely different at 0.3-volt. So we are starting with modeling the transistor behavior. It is not a full program," says Bert Gyselinckx, general manager of the Human Research program at IMEC.

For power efficiency, transistors turn off at the threshold voltage (Vt), and therefore limits the voltage scaling. Normally, this is a reduction of 0.2 volts, from 0.7-volt to 0.5-volt in modern CMOS processes. However, there is still some conduction after the power off; this leads to leakage and wasted energy. To save such energy, a transistor could be in operation in this sub-threshold region. 

This power-saving plan is not as easy as it sounds. Not all or applications will be suited for transistors operating below Vt. One problem for digital applications: lower frequency performance. Transistor operation is heavily dependent on variations in manufacturing, such as oxide thickness, junction depth, and body doping. Despite the hurdles, IMEC is concentrating their research on power-saving tactics. Medical appliances and biomedical applications are a focus of efforts, as well. Transistors are continually being upgraded in today's research labs. 

Gyselinckx said their goal is to power wireless electronic systems from built-up energy, currently offering around 100-microwatts of power. It is difficult to get even the simplest devices below 10-milliwatts, however. Therefore batteries are going to be hanging around for a long time, until that roadblock is overcome.

Future plans for Gyselinck's group includes producing short range RF transceivers, which would be ten times more power efficient than Bluetooth and Zigbee chips.