Twenty nanoseconds is very fast !
And you have not told us what the load is going to be.
Looking up the data sheet for your PFN60C mosfet, quoted turn on rise time is 170nS and fall time 130nS.
You have no hope of generating 20nS wide pulses with those.
This is going to be a very difficult project, and I suggest you do some internet research on "Pockles Cell drivers".
These are used to switch liquid crystal optical shutters at nanosecond speeds, and the liquid crystals require high voltage drive, and are a capacitive load, which makes it more difficult.