The widths of the base in a GaAs transistor and in a Si

The widths of the base in a GaAs transistor and in a Si transistor (both n-p-n type) are equal. GaAs transistor works at higher frequency—

1. The band gap of GaAs is higher than that of Si
2. The base transit time is lower in GaAs
3. The negative differential mobility in GaAs favours operational very high frequency
4. Si transistor works at higher frequency compared to GaAs transistor

The GaAs transistor works at higher frequency because the base transit time is lower in GaAs.