TFETs get a look from European energy researchers

Nov. 8, 2010
Project Steeple will try to squelch the power demands of electronic devices in Europe that are in stand-by mode.

European researchers are gearing up for project Steeper, which aims to boost the energy efficiency of home electronics, when active, by 10 times and virtually eliminate power consumption when they are in passive or standby mode.

Coordinated by Ecole Polytechnique Fédérale de Lausanne (EPFL), Project Steeper has involvement from IBM Research - Zurich, Infineon and Globalfoundaries, large research institutes CEA-LETI and Forschungszentrum Jülich, academic partners, University of Bologna, University of Dortmund, University of Udine and the University of Pisa and the managerial support of Sciprom.

To devise more efficient electronics, scientists on the project are looking at tunnel field effect transistors (TFETs) and semiconducting nanowires. The devices are seen as a way to drastically reduce semiconductor leakage currents. In Steeper, scientists not only hope to cut leakage current, but also to control current flow with less voltage as a way to get maximum efficiency.

According to the International Energy Agency (IEA), electronic devices currently account for 15% of household electricity consumption, and energy consumed by information and communications technologies as well as consumer electronics will double by 2022 and triple by 2030 to 1,700 Terawatt hours — equal to entire total residential electricity consumption of the US and Japan in 2009.

Standby consumption in the European Union is estimated to account for about 10% of the electricity use in homes and offices of EU member States. By 2020 it is expected that electricity consumption in standby/off-mode will rise to 49 terrawatt hours per year — nearly equivalent to the annual electricity consumption for Austria, Czech Republic and Portugal combined.

The development of novel devices, such as steep slope transistors from which the project gets its name, can provide a much more abrupt transition between the off and on states when compared with the current 60 mV/decade limit of metal–oxide–semiconductor field-effect transistors (MOSFETs) at room temperature. This mode of operation simultaneously allows for reducing the sub-threshold leakage and lowering the voltage at which circuits operate. The development of energy-efficient steep sub-threshold slope transistors that can operate at sub-0.5 V operation domain will be a critical factor in the success of the project.

Scientists will study the development of TFETs based on silicon (Si), silicon-germanium (SiGe) and III-V semiconducting nanowires, which allow optimum electrostatic control of the transistor channel. In a TFET quantum mechanical band-to-band tunneling is exploited to switch on the device and thus get a steeper turn-on characteristics compared to that of conventional MOSFETs.

Project Steeper will evaluate the physical and practical limits of boosting the performance of TFETs with III-V nanowires, and the resulting advantages for future energy efficient digital circuits.

The project started in June 2010 and will continue for 36 months.

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