Engineers from the University of California, Berkeley, describe a major breakthrough in the design of a component of transistors that could significantly reduce their energy consumption without sacrificing speed, size, or performance in a study published online in April 2022 in the journal Nature.
The component, known as the gate oxide, is responsible for turning the transistor on and off. “We have been able to show that our gate-oxide technology is better than commercially available transistors: What the trillion-dollar semiconductor industry can do today — we can essentially beat them,” said study senior author Sayeef Salahuddin, the TSMC Distinguished professor of Electrical Engineering and Computer Sciences at UC Berkeley.
This increase in efficiency is enabled through a phenomenon known as negative capacitance, which reduces the amount of voltage required to store charge in a material. In 2008, Salahuddin predicted the presence of negative capacitance theoretically, and in 2011, he demonstrated the effect in a ferroelectric crystal for the first time.
The research shows how negative capacitance may be obtained in an engineered crystal made up of a layered stack of hafnium oxide and zirconium oxide that is compatible with modern silicon transistors. The study demonstrates how the negative capacitance effect can greatly reduce the amount of voltage necessary to drive transistors, and hence the amount of energy spent by a computer, by introducing the material into model transistors.
Negative capacitance is achieved by carefully manipulating a material property termed ferroelectricity, which happens when a material produces an electrical field spontaneously. The researchers found that combining hafnium oxide and zirconium oxide in an engineered crystal structure termed a superlattice, which leads to simultaneous ferroelectricity and antiferroelectricity, can also produce negative capacitance.
“In the last 10 years, the energy used for computing has increased exponentially, already accounting for single digit percentages of the world’s energy production, which grows only linearly, without an end in sight,” Salahuddin said. “Usually, when we are using our computers and our cell phones, we don’t think about how much energy we are using. But it is a huge amount, and it is only going to go up. Our goal is to reduce the energy needs of this basic building block of computing, because that brings down the energy needs for the entire system.”
Read the entire study here.