They achieved this by combining a transistor with high-performing ferroelectric RAM memory technology. Until now, say the researchers, combining a ferroelectric material and the silicon material used for transistors has remained a challenge, as a result of issues that happen at the interface of the materials. However, say the researchers, they found a way to overcome this.
“We used a semiconductor that has ferroelectric properties,” says Peide Ye, the Richard J. and Mary Jo Schwartz Professor of Electrical and Computer Engineering at Purdue. “This way two materials become one material, and you don’t have to worry about the interface issues.”
The result, say the researchers, is a ferroelectric semiconductor field-effect transistor (FET), built in the same way as transistors currently used on computer chips. In addition to its ferroelectric properties, the material used by the researchers, alpha indium selenide, addresses the issue of a conventional ferroelectric material usually acting as an insulator rather than a semiconductor due to its much smaller band gap.
After building and testing the transistor, the researchers found that its performance was comparable to existing ferroelectric field-effect transistors, and could exceed them with more optimization. The researchers also worked with researchers at the Georgia Institute of Technology to build alpha indium selenide into a space on a chip – called a ferroelectric tunneling junction – which engineers could use to enhance a chip’s capabilities.
In the past, say the researchers, engineers had not been able to build a high-performance ferroelectric tunneling junction because its wide band gap made the material too thick for electrical current to pass through. With its much smaller band gap, alpha indium selenide can be just 10 nanometers thick, allowing more current to flow through it.
More current, say the researchers, allows a device area to scale down to several nanometers, making chips more dense and energy efficient. A thinner material – even down to an atomic layer thick – also means that the electrodes on either side of a tunneling junction can be much smaller, which would be useful for building circuits that mimic networks in the human brain.
For more, see “A ferroelectric semiconductor field-effect transistor.”