What if Silicon Valley moved beyond silicon? In the 80’s, Seymour Cray was asking the same question, delivering at Supercomputing 1988 a talk titled “What’s All This About Gallium Arsenide?” The supercomputing legend intended to make gallium arsenide (GaA) the material of the future for supercomputing, but unforeseen complications with the material made the Cray-3 his first and last major application of GaA. Now, 27 years after the Cray-3 launched, MIT researchers may have found an avenue for viably using gallium arsenide in future nonsilicon transistors.
The new discovery hinges on an alloy of gallium arsenide: indium gallium arsenide (InGaA). Electrons move quickly through InGaA alloys, and InGaA transistors are able to operate at low voltages, imbuing the material with a theoretical ability to enable smaller and more efficient transistors as compared to silicon. However, owing to those ostensible benefits, the alloy had been studied previously – and those researchers had concluded that InGaA was unreliable at such small scales.
Now, MIT researchers have discovered that these properties were not intrinsic to the material, but rather a result of a phenomenon called oxide trapping.
“A transistor is supposed to work as a switch,” explained Xiaowei Cai, lead author of the study, in an interview with MIT’s Daniel Ackerman. “You want to be able to turn a voltage on and have a lot of current. But if you have electrons trapped [as a result of oxide trapping], 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.”
Further, the team discovered that if the rate of electric signals through the transistor were kept above 1 GHz, oxide trapping was no longer an issue – they had only appeared degraded at lower frequencies.
Now, Cai describes the impression that InGaA is unstable for small-scale applications as a “misconception,” adding that the team believes “this is a problem that can be solved or engineered out of.”
“When we operate these devices at really high frequency, we noticed that the performance is really good,” Cai said. “They’re competitive with silicon technology.”
“We’re really excited,” she continued. “We hope this result will encourage the community to continue exploring the use of InGaAs as a channel material for transistors.”
Gallium arsenide also hit the news recently thanks to work from the University of Tokyo, where researchers are working to develop a new kind of memory based on spintronics that uses a gallium arsenide-based ferromagnetic semiconductor.