Researchers at the University of California, Berkeley say they’re on track to enable ultra-low power computing applications through advancements in the efficiency of transistors.
Through the use of ferroelectrics — a type of material that can hold both a positive and negative electrical charge without voltage applied to it — a research team led by professor Sayeef Salahuddin demonstrated for the first time that the charge accumulated for a given voltage can be amplified, a phenomenon called negative “capacitance.”
The eventual result: improved chargers for electric cars, lighter consumer electronics and longer-lasting radio frequency communications equipment.
The researchers first created a capacitor by marrying a ferroelectric material, lead zirconate titanate (PZT), with an insulating dielectric, strontium titanate (STO).
Then they applied voltage to the structure. (As a control group, they also applied voltage to a layer of STO alone.) By comparing the amount of charge stored in both devices, the researchers found a “two-fold voltage enhancement” in the charge from the ferroelectric structure, Salahuddin says.
This demonstrates that it’s possible to reduce the minimum voltage necessary to store charge in a capacitor, thereby allowing for a reduction in the energy consumption and heat generation of conventional electronics.
For now, the experiment merely confirms that negative capacitance is a viable strategy to help overcome the power draw of existing transistors. The next step is to design transistors to incorporate ferroelectric materials, allowing the generation of more charge from less voltage and assisting the semiconductor industry in breaking through the microprocessor clock speed ceiling it reached in 2005.
“Transistors have not become as ‘fuel-efficient’ as they need to be to keep up with the market’s thirst for more computing speed, resulting in a cumulative and unsustainable increase in the power draw of microprocessors,” said researcher Asif Khan in a statement. “We think we can change that.”
Their research is published in the Sept. 12 issue of the journal Applied Physics Letters.
Rendering: Asif Khan/UC Berkeley