We have investigated the electrical properties of heavily arsenic implanted GaAs, which has structural properties similar to low temperature GaAs. The electrical conduction in the lateral direction is dominated by hopping in a defect band and the resistivity after a 600 °C anneal is on the order of 103&OHgr; cm. However, the resistivity measured on ann‐i‐nstructure in the direction perpendicular to the surface is on the order of 109&OHgr; cm. This huge difference in resistivity can be explained by the lack of an electrical contact to the defect band in then‐i‐nstructure. The activation energy of the resistivity in then‐i‐nstructure is 0.74 eV. This value is close to that for bulk undoped semi‐insulating wafers, in which the Fermi level is pinned at the midgap donor, EL2. A current transient spectroscopy study of this material reveals an electron trap with an activation energy of 0.82 eV, identical to the EL2. ©1995 American Institute of Physics.