Researchers at Purdue University have made progress towards an elusive goal: building a transistor that can both process and store information. In the future, a single on-chip component could integrate the processing functions of transistors with the storage capabilities of ferroelectric RAM, potentially creating a process-memory combo that enables faster computing and is just atoms thick.
The ability to cram more functions onto a chip, allowing for greater speed and power without increasing the footprint, is a core goal of electronics design. To get where they are today, engineers at Purdue had to overcome incompatibilities between transistors – the switching and amplification mechanisms used in almost all electronics – and ferroelectric RAM. Ferroelectric RAM is higher-performing memory technology; the material introduces non-volatility, which means it retains information when power is lost, unlike traditional dielectric-layer-constructed DRAM.
In the past, materials conflicts have hampered the design of commercial electronics that integrate transistors and memory. “Researchers have been trying for decades to integrate the two, but issues happen at the interface between a ferroelectric material and silicon, the semiconductor material that makes up transistors. Instead, ferroelectric RAM operates as a separate unit on-chip, limiting its potential to make computing much more efficient,” Purdue explains in a statement.
A team of engineers at Purdue, led by Peide Ye, came up with a solution: “We used a semiconductor that has ferroelectric properties. This way two materials become one material, and you don’t have to worry about the interface issues,” said Ye, who is a professor of electrical and computer engineering at the university.
The Purdue engineers’ method revolves around a material called alpha indium selenide. It has ferroelectric properties, but it overcomes a limitation of conventional ferroelectric material, which generally acts as an insulator and doesn’t allow electricity to pass through. The alpha indium selenide material can become a semiconductor, which is necessary for the transistor element, and a room-temperature-stable, low voltage-requiring ferroelectric component, which is needed for the ferroelectric RAM.
Alpha indium selenide has a smaller band gap than other materials, the university explains. Band gaps are where no electrons can exist. That shrunken band gap, found in the material natively, means that material isn’t a serious insulator and isn’t too thick for electrical current to pass through — yet there is still a ferroelectric layer. The smaller band gap “[makes] it possible for the material to be a semiconductor without losing ferroelectric properties,” according to Purdue.
“The result is a so-called ferroelectric semiconductor field-effect transistor, built in the same way as transistors currently used on computer chips.”
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