silicon wafer

MIT study suggests promise for non-silicon transistors

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An MIT study has demonstrated that deterioration in the performance of InGaAs (indium gallium arsenide) transistors at small scales is not an intrinsic property of the material.

For computing power to continue to improve into the future, supporting more computationally expensive processes, engineers will need to develop ever-smaller and more densely packed transistors. For decades, silicon has been the semiconducting material of choice for transistors. However, InGaAs has been pitched as a potential competitor to silicon.

InGaAs has excellent electron transport properties and transistors made with the alloy can process signals quickly, potentially unlocking speedier calculations. They can also operate at relatively low voltages, potentially enhancing energy efficiency. However, its electron transport properties seem to deteriorate at the nanoscale, leading some researchers to conclude that the material is not suitable for the task.

MIT researchers have now discovered that this is a misconception; this apparent deterioration is not an intrinsic material of InGaAs itself.

The team found that its small-scale performance issues are at least in part due to oxide trapping. This phenomenon causes electrons to become stuck while flowing through a transistor.

“A transistor is supposed to work as a switch. You want to be able to turn a voltage on and have a lot of current,” said Xiaowei Cai, lead author of the study. “But if you have electrons trapped, what happens is you turn a voltage on, but you only have a very limited amount of current in the channel, so the switching capability is a lot lower when you have that oxide trapping.”

Oxide trapping was identified as the cause of performance loss by studying the frequency dependence of the transistor: the rate at which electric pulses are sent through the transistor. At low frequencies, the performance of nanoscale InGaAs transistors appeared degraded, while at frequencies of 1GHz and above oxide trapping was no longer a hindrance.

“When we operate these devices at really high frequency, we noticed that the performance is really good. They’re competitive with silicon technology,” Cai said.

The finding could reignite interest in InGaAs transistors, potentially push computing power and efficiency beyond what is possible within the limits of silicon: “We hope this result will encourage the community to continue exploring the use of InGaAs as a channel material for transistors,” Cai said.

“This [research] area remains very, very exciting. We thrive on pushing transistors to the extreme of performance,” said Professor Jesús del Alamo, who worked with Cai on the study.

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