Purdue University engineers have developed a way that the millions of tiny switches used to process information — called transistors — could also store that information as one device. The method, detailed in a paper published in Nature Electronics, accomplishes this by solving another problem: combining a transistor with higher-performing memory technology than is used in most computers, called ferroelectric RAM.

a, Schematic of a Fe-FET. b, Schematic of a FeS-FET. In the FeS-FET, the conventional semiconductor channel is replaced by a ferroelectric semiconductor, while the gate insulator is still conventional dielectric. c, Polarization bound charge distribution in a FeS-FET in polarization down (after negative gate bias) and polarization up (after positive gate bias) states.

The material, alpha indium selenide, not only has ferroelectric properties, but also addresses the issue of a conventional ferroelectric material usually acting as an insulator rather than a semiconductor due to a so-called wide “band gap,” which means that electricity cannot pass through and no computing happens. Alpha indium selenide has a much smaller band gap, making it possible for the material to be a semiconductor without losing ferroelectric properties.

In the past, researchers hadn’t 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. Since alpha indium selenide has a much smaller band gap, the material can be just 10 nanometers thick, allowing more current to flow through it. More current allows a device area to scale down to several nanometers, making chips more dense and energy efficient, Ye said. 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.

Source (Purdue University. “Reorganizing a computer chip: Transistors can now both process and store information: Researchers solve decades-old challenge of building a functional transistor integrated with ferroelectric RAM.” ScienceDaily. ScienceDaily, 9 December 2019.)

Paper: Mengwei Si, Atanu K. Saha, Shengjie Gao, Gang Qiu, Jingkai Qin, Yuqin Duan, Jie Jian, Chang Niu, Haiyan Wang, Wenzhuo Wu, Sumeet K. Gupta, Peide D. Ye. A ferroelectric semiconductor field-effect transistor. Nature Electronics, 2019; DOI: 10.1038/s41928-019-0338-7