Ion implantation in gallium arsenide (GaAs) has been extensively investigated for the VLSI industry and for the realisation of novel electronic devices such as micro and millimetre wave applications. A general advantage of ion-implantation induced electrical isolation is the lateral selectivity and preservation of surface planarity. In the present work, we systematically study the electrical isolation of n-type GaAs devices by single energy MeV/MeV-like implantation in which a constant level of damage caused by the isolating ion specie is maintained throughout the doped layer. It is observed that the maximum sheet resistivity values are dependent on sufficient damage accumulation in the layer for a specific isolation scheme. It is also found that the threshold dose (Dth) to convert the n-type GaAs layer to a highly resistive one closely correlates with the estimated number of simulated lattice atomic displacements (Nd) along the conductive region. Moreover, for identical samples, atomic mass of the implanted specie increases with the decrease of the threshold dose.