Engineers are paving the way for chip components that could serve as both RAM and ROM

Year after year, the explosive growth in computing power relies on the ability of manufacturers to integrate more and more components into the same space on a silicon chip. These advancements, however, are now approaching the limits of the laws of physics, and new materials are being explored as potential replacements for silicon semiconductors long at the heart of the computer industry.

An illustration and electron microscope image of the researchers’ FE-FET device. (Image: Penn Engineering today)

New materials may also enable entirely new paradigms for individual chip components and their overall design. A long-promised advancement is the Ferroelectric Field Effect Transistor, or FE-FET. Such devices might change state quickly enough to perform calculations, but also be able to maintain those states without being powered, allowing them to function as long-term memory storage. Serving as both RAM and ROM, FE-FET devices are said to make chips more efficient and powerful.

The barrier to making practical FE-FET devices has always been in manufacturing; the materials which best exhibit the necessary ferroelectric effect are not compatible with mass production techniques of silicon components due to the high temperature requirements of ferroelectric materials.

Today, a team of researchers from the School of Engineering and Applied Sciences has shown a potential way around this problem. In a pair of recent studies, they demonstrated that scandium-doped aluminum nitride (AlScN), a material recently discovered to exhibit ferroelectricity, can be used to make FE-FET as well as memory devices from diode-memristor type with commercially viable properties. .

The studies were led by Deep Jariwala, assistant professor of electrical and systems engineering (ESE), and Xiwen Liu, graduate student in his lab. They collaborated with Troy Olsson, also Assistant Professor at ESE, and Eric Stach, Professor in the Department of Materials Science and Engineering and Director of the Structure of Matter Research Laboratory.

They published their findings in journals Nano letters and Letters of Applied Physics.

“Engineers have been pursuing the concept of FE-FET memory since the 1960s, because these devices could operate at extremely low powers,” Jariwala explains. “The problem was really to make them compatible with processors and make them last longer. This is where our 2D materials come in; they’re so thin that once a bit of memory is written to them, they could hold that information as a charge for years.

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Richard V. Johnson