Transistors made from different semiconductors have pros and cons:
Si has a smaller bandgap and high electron mobility. Hence, Si transistors naturally suit high frequency but small signal applications(CPU, MOSFET etc.) unless compromised designs (such as drift regions) are adopted to increase working voltage with reduced working frequencies (IGBT, LDMOS et al). However, for widely-used IGBT, the recombination of holes and electrons limits the switching frequency and causes energy loss.
SiC MOSFETs have advantages over Si IGBT for EV applications because the single-polar nature results in efficient EV modules of high switching efficiency. But Tesla's reduced deployment of SiC MOSFET for some of its future model may indicate that the costs of EV modules are high, because the small channel electron mobility ( < 1/5 the value of Si IGBT) and on-state characteristics at high current may lead to expensive module design and packaging.
GaAs-based transistors consist of III-V layered structures (such as AlGaAs/GaAs) grown on semi-insulating GaAs substrates by MBE. But limited by the thermal conductivity of GaAs, the transistors suit small to mid power RF applications (< 2W/mm) .
GaN/SiC high electron mobility transistors(HEMT) suit both high frequency (4G/5G/6G) and high power RF applications (5G/6G masts and mobile phone frontend circuit et al). However, the commercial applications have been hindered not only by the high cost of semi-insulating SiC substrates but also by material defects that may cause transistor degrading over time.
Communication and EV technologies will exist forever with human activities on this planet and the developments of these technologies will never come to an end although the R & D activities have been shifted from universities to industry over the last half century. GSD's technologies aim to address some of the issues.