Cubic boron arsenide provides thermal material boost

Technology News |
By Nick Flaherty

Researchers at MIT and the University of Houston have investigated the properties of cubic boron arsenide (C-BAs) for high performance power semiconductors.

The material has a higher mobility for both electrons and holes than silicon at >1000 cm2/Vs as well as 10x the thermal conductivity at 1200 W/mK, third only to diamond and boron nitride.

However the process for making the material is extremely limited. “This potentially could be really important, and people haven’t really even paid attention to this material,” said MIT professor of mechanical engineering Gang Chen.

The researchers had to use special methods originally developed by former MIT postdoc Bai Song to test small regions within the material and they say more work will be needed to determine whether cubic boron arsenide can be made in a practical, economical form.

Earlier experiments showed that the thermal conductivity of cubic boron arsenide is almost 10 times greater than that of silicon. “So, that is very attractive just for heat dissipation,” said Chen.

The new work fills in details on the mobility for both electrons and holes. “That’s important because of course in semiconductors we have both positive and negative charges equivalently. So, if you build a device, you want to have a material where both electrons and holes travel with less resistance,” said Chen.

“Heat is now a major bottleneck for many electronics,” said researcher Jungwoo Shin at MIT. “Silicon carbide is replacing silicon for power electronics in major EV industries including Tesla, since it has three times higher thermal conductivity than silicon despite its lower electrical mobilities. Imagine what boron arsenides can achieve, with 10 times higher thermal conductivity and much higher mobility than silicon. It can be a gamechanger.”

“The critical milestone that makes this discovery possible is advances in ultrafast laser grating systems at MIT,” said Shin. Without that technique, he says, it would not have been possible to demonstrate the material’s high mobility for electrons and holes.

“We predicted the electron and hole quantum mechanical behavior, also from first principles, and that is also proven to be true,” said Chen. “This is impressive, because I actually don’t know of any other material, other than graphene, that has all these properties. And this is a bulk material that has these properties.”

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