Breakthrough semiconductor tech cuts power use by 1 billion times

A collaborative effort between researchers at the University of Pennsylvania, Massachusetts Institute of Technology (MIT), and the Indian Institute of Science (IISc) has made phase-change memory (PCM) more energy efficient and could unlock a revolution in data storage in the future, a press release said. 

PCM is a promising data storage technology that uses different material phases to store information. When materials change from their amorphous to crystalline state, they resemble an on/off switch, much like the binary system used for data storage today. 

PCM could be used to store information in devices such as cell phones and computers, but affecting the phase change is an energy-intensive process, which has remained a hurdle to large-scale deployment. 

In recent work published by the Indo-US collaboration, researchers achieved the phase change using one billionth of the energy previously required to work with material indium selenide (In2Se3), potentially starting a new revolution in data storage capabilities. 

Electric transformation

In the amorphous phase, the material’s atoms are arranged in random order. The process of changing a material to its amorphous phase is called amorphization, and it is conventionally achieved by melting it to its liquid state and then rapidly cooling it so that crystals cannot form. 

The melt-quench approach to amorphization is energy-intensive, but a decade ago, a research team led by Ritesh Agarwal at UPenn found that electric pulses could also achieve the same result in alloys of germanium, antimony, and tellurium. 

A few years ago, the research team expanded their work to include the semiconductor material indium selenide (In2Se3). Its ferroelectric property allows it to polarize spontaneously, while its piezoelectric nature generates electric current as a response to mechanical stress, which then deforms it rapidly. 

However, the researchers needed to be more certain about how this process occurs. 

Indian in-situ microscopy

Agarwal then sent samples of In2Se3 to Pavan Nukala, his former colleague at UPenn, now an assistant professor at IISc and a member of the Centre for Nano Science and Engineering (CeNSE). 

Nukala’s team built a suite of in-situ microscopy tools, which they used to analyze the amorphization process of In2Se3 closely. They found that it resembles both an earthquake and an avalanche. 

When an electric current passes through the material, tiny sections as small as a billionth of a meter begin amortizing. The material’s piezoelectric properties and layered structure nudge portions of In2Se3 into unstable positions, much like shifting snow on a mountaintop. 

At a critical point, the movement results in a spread of deformations, and as distorted regions collide, sound waves are generated in the material. The sound waves act like seismic waves moving the earth during an earthquake, resulting in more deformation and the creation of new amorphous areas, leading to an avalanche. 

“It’s just goosebump stuff to see all these phenomena interacting across different length scales at once,” said Shubham Parate, a doctoral student at IISc, who was involved in the work. 

“This opens up a new field on the structural transformations that can happen in a material when all these properties come together,” added Agarwal in the press release. “The potential of these findings  for designing low-power memory devices are tremendous.”

The research findings were published in the journal Nature.