ABSTRACTRemarkably good device performance at both dc and microwave frequencies has recently been obtained from GaAs based devices grown on Si substrates. In GaAs MESFETs on Si, current gain cutoff frequencies and maximum oscillation frequencies of fT = 13.3 GHz and fmax = 30 GHz have been obtained for 1.2μm devices, which is nearly identical to the performance achieved in GaAs on GaAs technology for both direct implant and epitaxial technology. For heterojunction bipolar transistors, current gain cutoff frequencies and maximum oscillation frequencies of fT = 30 GHz and fmax = 11.3 GHz have been obtained for emitter dimensions of 4×20μm2. In GaAs AlGaAs MODFETs. current gain cut-off frequencies of about 15 GHz with lμm gates were obtained on GaAs and Si substrates. The pseudomorphic InGaAs/GaAs MODFETs were also fabricated and found to be comparable to GaAs MODFETs although they should perform better. The structures were also shown to maintain their properties when put through ion implantation and annealing process. Given the performance already demonstrated in GaAs on Si devices and the advantages afforded by this technology, the growth of III-Vs on Si promises to play an important role in the future of heterojunction electronics.