Researchers from MIT and elsewhere have found a material that can perform much better than silicon. They say the next step is finding practical and economic ways to manufacture it.
Silicon is one of the most plentiful elements on Earth, and in its pure form, the semiconductor material has become the foundation of much of modern technology, including microelectronic computer chips and solar cells. However, silicon’s properties as a semiconductor are actually far from ideal.
Now, a team of scientists from MIT, the University of Houston, and other institutions has carried out experiments showing that a material called cubic boron arsenide overcomes two limitations of silicon:
Although silicon allows electrons to readily flow through its structure, it is much less accommodating to “holes” — electrons’ positively charged counterparts —and harnessing both is crucial for particular types of devices.
Silicon does a poor job of transporting heat, which contributes to the frequent overheating problems and pricey cooling systems in computers.
In addition to providing high mobility to both electrons and holes, cubic boron arsenide has excellent thermal conductivity. It is the best semiconductor material ever found, and maybe the best possible one, according to the researchers.
Cubic boron arsenide has so far only been made and tested in small, lab-scale batches that are not uniform. In fact, in order to test small regions within the material, the scientists had to use special methods. More work will be needed to determine whether cubic boron arsenide can be made in a practical, economical form, much less replace the ubiquitous silicon. But even in the near future, the researchers say, the material could find some uses where its unique properties would make a significant difference.
The findings were reported on July 21, 2022, in the journal Science, in a paper by MIT postdoc Jungwoo Shin and MIT professor of mechanical engineering Gang Chen; Zhifeng Ren at the University of Houston; and 14 others at MIT, the University of Houston, the University of Texas at Austin, and Boston College.
Silicon has good electron mobility but poor hole mobility, and other materials such as gallium arsenide, widely used for lasers, similarly have good mobility for electrons but not for holes.
Researchers say the challenge now is to figure out practical ways of making this material in usable quantities. The current methods of making it produce very nonuniform material, so the team had to find ways to test just small local patches of the material that were uniform enough to provide reliable data.