High mobility of electrons, the possibility of formation of semi-insulating layers excites an interest to GaAs. The implantation of donor impurities into semi-insulating GaAs:Cr has a great practical application, allowing to create the conducting suhnicrcn layers. To obtain the functional suhmicron n+-layers one uses mainly the implantation of ions of Si, that accounts for its small mass and the lack of the necessity for irradiation at higher teMperatures. Silicon is the amphoteric impurity in GaAs. At low doses ≤1013 Cm−2 it behaves as donor inpurity with the high level of activation, though at the increase of the implantation dose some of the siliccn atoms begin to substitute arsenic and in this position they display the properties of acceptor impurity, leading to self-compensation. Its amphoteric properties were shown with the help of As+Si and Ga+Si double implantation [1]. The increase of activation of Si, as donor impurity, can be obtained by double implantation of 31p+28Si [2]. Phosphorus has atomic mass close to Si, it is isoelectronic to As and does not cause compensation effect in GaAs up to the doses ≃1015 cm−2. Moreover double implantation allows to vary the magnitude of the diffusion coefficients of impurities.