GaAs p-type vs Si n-type Mosfet frequency
how the frequency can be calculated

You can't because:

&quot;the frequency&quot; means nothing, what you might want to know is the \$f_t\$ of the devices. The \$f_t\$ is the frequency at which the transfer function (usually not gain but transconductance!) of the device starts to drop with increasing frequency. Read this.

GaAs and Silicon transistors are quite different in their buildup, so even if devices have the same dimensions it doesn't mean that the comparison is a fair one. One technology might allow you to make very small and very fast transistors while in the other technology the transistors must be much larger (otherwise they don't work) yet these large transistors could be much faster than the other (very small) ones.

In general in GaAs technology the fastest transistors can be made. This is because the electron mobility is much greater in GaAs. However, Silicon CMOS is catching up because devices can be made extremely small. Also complex functions are much easier to implement in CMOS while GaAs is somewhat limited in that respect. You want a small microcontroller? No issue in CMOS, but large and therefore expensive in GaAs.


So, stop trying to calculate and looking for formulas. Understanding how and why is much more important.