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Therefore silicon dioxide has been replaced by hafnium dioxide (a part of the hafnium may be substituted with zirconium or rare-earth elements), which has a much higher dielectric constant, and which is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.

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.

They won't tell anyone

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.

The first roadblock on the use of new semiconductor materials is that in the beginning nobody succeeds to make crystals that are both big enough and free enough of defects. For size, usually achieving to make 2-inch wafers is the threshold for enabling commercial applications.

The second problem is finding metallization systems that can achieve ohmic contacts and rectifying contacts on the semiconductor crystal and the third is finding impurities that allow to modify the polarity and the concentration of the charge carriers in wide enough ranges.

These 2 problems are particularly difficult for wide-bandgap semiconductors, like gallium nitride, but they are unlikely to be difficult for indium selenide, which should behave similarly to zinc selenide or indium phosphide, for which there is much more experience.