Quoting William Huo, InSe outperforms silicon in every category that matters:
• 5–10x higher electron mobility
• Atomic thickness
• Tunable bandgap
• Lower power leakage
• Faster switching
So how big of news is this?
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There are vast lists of "better than silicon" semiconductor crystals. Most good power mosfets these days are gallium nitride, for example.
Where they all fail is production process, which amounts to transistor size, basically. Sure, you can make a really great, very efficient, measurably improved very much macroscopic transistor. But no one knows how to put a hundred billion of them on a chip, so... basically who cares?
Someday someone will figure it out, maybe. But announcing an exciting new chemistry says little to nothing.
The problem is not the transistor size, but the transistor cost.
It is easy to make transistors as small as on silicon on most other semiconductors, but the cost of the final product would be many times greater.
One important reason is that silicon is made into huge 12-in wafers, while most other semiconductors are made into small 2-inch to 4-inch wafers, like for silicon several decades ago. At each processing step on a silicon production line one machine processes 9 to 36 times more transistors than if another semiconductor were used. Large wafers also waste much less area when making big dies.
In general, for silicon there exist very big processing machines with very high productivity, while for other materials there is little difference between lab equipment and what can be used for commercial production. An integrated circuit made on a non-silicon material also requires more processing steps and more expensive materials.
In order to keep increasing the performance of CPUs and GPUs, the replacement of silicon with another semiconductor is unavoidable, perhaps in a decade from now. However, that will be done only after all other possibilities of improving silicon devices will be completely exhausted, in order to avoid the increase in production costs.
> It is easy to make transistors as small as on silicon on most other semiconductors
Yikes, [citation needed] here. No, it absolutely is not. All the etch and litho chemistry is highly specific to the substrate and dopants. You can't just feed a germanium crystal through an etcher tool in a TSMC fab and get anything but a brick out the other side.
I'm not aware of anyone anywhere doing low-nm lithography on anything but silicon (even in a demo context, or even announcing plans for the capacity), but I'm willing to be educated.
Nobody has done low-nm lithography on anything but silicon, on integrated circuits.
The reason is that such integrated circuits could not compete in cost, so developing all the fabrication equipment for them would not be worthwhile.
On the other hand, on special discrete devices, e.g. microwave transistors, and on experimental devices, "low-nm" (which means tens of nm for the most advanced devices) has been done for a long time.
The low fabrication yields, which would be unacceptable for the mass production of integrated circuits, have much less relevance for small and expensive discrete devices and for experimental devices.
This does not appear to be an ingot, as silicon would be prior to being cut, but a film grown on some substrate, itself called a "wafer," so perhaps silicon?
The film itself is one atomic layer in thickness?
I don't know how you would make "wells" that form a FET, either for the source and drain, or for the larger complimentary wells of CMOS.
I don't know how advanced the thinking is to do this, or an equivalent.
Many semiconductor materials cannot be grown as ingots that are later cut into wafers, like it is done with silicon or germanium, but they are grown epitaxially as thin layers on wafers made of other semiconductor or insulator materials that have a compatible crystal structure.
Most gallium nitride devices, like those that are used now in miniature chargers for laptops/smartphones, are made like this.
Using this technique for indium selenide is a standard procedure, not something surprising.
The "wells" are made by doping with various kinds of atoms, which is normally done by ion implantation, i.e. a ion beam inserts the desired impurities into the crystal, at the desired depth.
In very thin devices, like in most modern CMOS technologies, the doped zones no longer look like "wells". For an N-channel MOSFET, you just have from source to drain 3 zones of alternating polarity, n-p-n. The middle zone is surrounded partially or even totally by the gate insulator.
What's the story for an insulator? Silicon's pretty awesome, but in many ways silicon dioxide (grown in place) is the real magic.
Unfortunately, even if the thermally-grown silicon dioxide is what has enabled the appearance of the monolithic integrated circuits and of the MOSFET transistors, eventually it had to be replaced.
There are already around two decades since silicon dioxide is no longer used as the gate insulator in high-performance transistors. The reason is that its dielectric constant is too low, so for very small transistors the gate would have to be too thin, so thin that it is impossible for it to not have holes and also impossible to prevent electrons from tunneling through it.
Therefore silicon dioxide has been replaced by hafnium dioxide (a part of the hafnium may be substituted with zirconium or rare-earth elements), which has a much higher dielectric constant, and which is also chemically resistant enough to survive the following wafer processing steps.
Because HfO2 cannot be grown in place, but it must be deposited in its entirety, it is much more difficult to ensure that the insulator-semiconductor interface is perfect, but the industry had to solve this problem decades ago, otherwise it would have been impossible to make the transistors smaller.
For other semiconductors than silicon, the gate insulator always had to be deposited. Because this is hard, metal-insulator-semiconductor FETs not made of silicon or of silicon carbide had only very rarely been used in the past. The transistors that are not made of Si or SiC typically are either Shottky-gate FETs or heterojunction bipolar transistors.
I vastly underperforms silicon in the most important category: cost.
Looks like indium is about $390/kg. That is not cheap, but does not seem significant given how much material goes into a high performance CPU.
The reserves of indium are extremely small. Any new use that would increase demand would also increase the price. Also that price is for commercially pure indium. After indium is purified enough to be usable in semiconductor devices the price increases many times, possibly much more than 10 times.
Currently, the major consumers of indium are all the screens for monitors, laptops and smartphones, which use indium oxide as a transparent conductor, then the LEDs used in lighting and indicators. Also the power devices with gallium nitride contain indium, and their use is increasing.
There exist no mines of indium. Indium can be obtained as a byproduct from the extraction of other metals, primarily from zinc mining, but its concentration in zinc minerals is very small.
In order to produce more indium, one also has to produce more zinc, in an amount several orders of magnitude greater than the amount of produced indium. When the demand from indium will exceed that available from the current zinc production, further increases in demand will increase the indium price much steeper.
Except for indium, among the other chemical elements only for the platinum-group metals there is a so great mismatch between the amount that would be required by potential applications and the amount that is available on Earth. Selenium and tellurium are also close of these from this point of view.
Well if it's used as a thin film on screens, it wouldn't require much more production to make a few square centimeters more for chips to build a computer to use that screen.
We also ramped production of those screens without some major supply chain problem requiring 10x zinc production.
I don't see scarcity as a problem.
Wait for Chinese to find a (mostly) aluminum based III-V/VI
They won't tell anyone
Literally world changing