What is the highest maximum voltage for a high voltage FET or other transistor? I do not need to be able to buy it, just want to know the voltage it can handle.
I was searching the internet and found that I couldn't find any real high voltage FETs or other transistors. The highest I could find where between 3000 and 9000 V.
Are there actual transistors or MOSFETs for higher voltage out there for example in specialized machinery? The around 9000 V versions were experiments in universities.
For highest voltage per device you'll have to look into "vacuum state transistors" (ie, tubes) like Thyratrons, or even not-so-vacuum-filled valves like the Mercury Arc Rectifier, which is basically a thyristor. Voltage is somewhat unlimited since it depends on the length of the arc tube.
At high voltage, you will find mostly thyristors and diodes, because the main application is switching and rectifying. An actual amplifier would require something like transistors, or triode/pentode tubes, but few are actually interested in 300kV output amplifiers...
What determines breakdown voltage is the length or thickness of the insulator, so for transistors this is limited to what is possible to manufacture and of course to what customers will buy. The whole point of semiconductors is that they're tiny so you can manufacture a lot of them cheaply on a wafer, but this results in insulation/creepage distances that are not compatible with hundreds of kV.
Theoretically it should be possible to build almost unlimited voltage triodes for that juicy Class-A sound. After all it's a glass tube, you can make it one meter long for the extra insulation distance. But that would be "special order".
For higher voltages series combinations of individual semiconductor devices (IGBTs and thyristors, usually) are used to handle things like a 275kV DC input that must be converted to 3-phase AC. Individual devices are probably in the 4-9kV range, you could probably find out with a bit of research.
There are some experimental devices in the 15kV range for SiC IGBTs but they may not be possible to buy.
If you have a specific problem to solve, you should look at solving it with easily available mature technology as a first step.
So for those wanting to actually use something like that themselves. this: https://youtu.be/HIUtZSaXuow is the device I designed/made I still have to add its functional description. however, this holds enough information to reproduce it. and I think it is quite simple for people to come up with how it works for themselves + I am mostly visual-based which makes such things a lot harder to explain in words since I see the fields, etc.
but it is basically a simple transistor for high voltages which you can make from basically any materials. you have 2 terminals with a spark gap and one of 2 types of capacitor plate/material below it. you get some things like static push/pull energy flow which wants to keep going after stopping and a partly virtual voltage rise.
it is no diode-based transistor, but you can easily modify it to work as a diode. this requires a specific additional piece which in turn can turn as many of those in diodes as you like to.
This is not about commercially available stuff, but it is something any hobbyist could make if it needs a very high voltage transistor
