Has MIT found the ultimate semiconductor?

The shortage of semiconductors has once again reminded us how important these materials are to our species. the siliconin particular, is absolutely ubiquitous; we find in the all computer chipsfrom your connected watch to the largest supercomputers in the world.

However, this almost ubiquitous material is far from ideal at all levels. For starters, its thermal conductivity is anything but exceptional; it is for this reason that your computer needs to be constantly cooled.

At least it conducts electrons extremely well. But contrary to what intuition suggests, this does not mean that its electrical conductivity is more ideal. Indeed, silicon is much less accommodating for so-called electron “holes”.

It is a physical concept where the absence of an electron is treated as a particleand the latter must imperatively be free of their movements so that a semiconductor can play its role. ” It’s important because when you build a device, you want to have a material where the electrons, but also these holes travel without resistance “, explains Gang Chen, co-author of a new study on the subject.

One semi to drive them all

He and his team at the prestigious MIT recently conducted a series of experiments on a material with simply exceptional semiconductor properties: boron arsenide crystallized in cubic form (c-BA). To begin with, it presents a phenomenal thermal conductivityalmost 9 times greater than that of silicon (1300 W/mK against 149 W/mK at 28°C).

But this very interesting property had already been documented by researchers in materials science. On the other hand, what these previous works failed to show is that c-BA also offers a exceptional mobility to electrons and these famous “holes”.

For these reasons, the researchers claim that it is simply the ” best semiconductor ever found, and possibly the best possible ! ” It’s impressive, because I don’t know of any other material, apart from graphene, that brings together all these properties. says Chen.

” Temperature is a major bottleneck for many electronic devicess,” says Jungwoo Shin, lead author of the study. “ Silicon carbide replaces simple silicon in many major industries, such as electric vehicles with Tesla thanks to its 3x higher thermal conductivity, despite the fact that electronic mobility is less important there “, he details.

“ Imagine what we could achieve with cubic boron arsenide, with ten times greater thermal conductivity, but also much greater electronic mobility! It could change everything “, he breathes.

A potential as enormous as its industrial limits

Note that it is no coincidence that the researcher uses the conditional. Certainly, the c-BA is a marvel of materials science. But it is also immensely more difficult to domesticate than our good old silicon.

First limit, and not least: boron arsenide is far from being as abundant as silicon. Moreover, its synthesis in crystalline form is extremely complicated. Even for manipulators of great talent who have access to advanced equipment. Most of the time, these crystals have large structural defects that would prevent them from exploiting their full conductive potential.

The other concern is the purity of the material. Today, silicon is very well known; over several decades of uninterrupted research, the industry has learned to produce it with a purity of approximately 99.99999999% (we speak of ” ten nines “). And for the moment, the researchers do not yet have the shadow of an idea that would allow them to achieve a score even comparable with cubic boron arsenide.

And even if they manage to work around these problems, they won’t be out of the inn. They will still have to answer a lot of fundamental questions before considering industrial use. The most important of these concerns the stability and the sustainability of this material.

Despite all the faults of silicon, the industry knows that it remains stable; she can count on it for years. And it is a determining factor at absolutely all levels (supply, storage, lifespan, price, etc.).

Future prospects still unclear

Even ignoring its other limitations, cubic boron arsenide could not be used on a large scale until manufacturers knew exactly how it behaves over time — and by extension, how badly it can be commendable.

Suffice to say that it is not tomorrow the day before that a new semiconductor will come to replace silicon; it will take more than a hugely promising material to convince an entire industry to replace the bedrock it has stood on for decades.

” Silicon is the workhorse of the industry sums up Chen. ” Ok, we have a material that is simply better. But will it move the industry? We don’t know. “Even though it does look like the ideal semiconductor on paper, ” if it can actually end up in a device and replace some of the current market… i think that is still to be proven “, he concludes.

The text of the study is available here.