comparison between GaAs and silicon technology

Gallium-Arsenide (GaAs) has historically been the preferred technology for PAs because of its intrinsically higher low-field electron mobility, transistion frequency (ft 1) and breakdown voltage. The semi-insulating GaAs substrate also helps in developing high-Q passive elements. Due to higher bandgap energies and mobilities, GaAs PAs have higher gain even at lower operating voltage. The higher gain translates into improved Power Added Efficiency (PAE) as compared to Si or SiGe PA’s. figure summarizes the key relative differences between Si and GaAs for RF applications . 1The theoretical frequency at which the short circuit current gain of the CE mode transistor drops to 0dB. Even though GaAs has a number of advantages over Si, it also has some disadvantages which needs to be considered. The thermal conductiviy of GaAs is about 4 times lower than that of Si. This is a particularly difficult challenge for GaAs ICs as the power which must be dissipated is typically higher than that of Si ICs. Thermal management issues is a major consideration with regards to the ruggedness of the GaAs PAs. Stability and reliability have also been areas of major concern in GaAs technology