Arsenic precipitates can be formed in GaAs using arsenic implantation and annealing, thereby producing very high resistivity (surface or buried) GaAs layers. Arsenic-implanted materials are similar to low-temperature (LT) GaAs:As buffer layers grown by molecular beam epitaxy (MBE) which are used for eliminating side- and backgating problems in GaAs circuits. Arsenic implantation is not only a simple and economical technique for device isolation but also can improve the quality of individual devices. Through surface passivation, arsenic implantation can reduce gate-to-drain leakage in and enhance the breakdown voltage of GaAs-based metal semiconductor field-effect transistors (MESFETs) and high electron mobility transistors (HEMTs). High resistivity thin surface layers may be used as gate insulators for GaAs-based metal insulator semiconductor (MIS) FETs, leading to the development of a novel GaAs-based complementary metal insulator semiconductor (CMIS) technology like advanced Si-based complementary metal oxide semiconductor (CMOS) technology but with higher radiation hardness and operational speed.