Combined use of TEM and DSL photoetching (Diluted Sirtl-like etchant with Light) has been employed to investigate the origin of DSL etch features in ion implanted GaAs. The undoped, semi-insulating (001) LEC GaAs wafers were implanted with 29Si with fluences varying between 1.5-1012 and 3.0-1014 at/cm2. After implantation, rapid thermal annealing (RTA) was carried out at 900 °C for 10 s.The implantation damage was revealed by DSL in the form of microroughness in both as-implanted and annealed samples. The degree of microroughness varied according to the implantation dose and to whether the sample was as-implanted or annealed. A calibration by TEM was, thus, carried out in order to establish the nature of the underlying defects and the threshold implantation dose for their formation. To avoid the influence of the as-grown dislocations on the formation of the DSL etch features due to ion implantation, a shallow DSL photoetching was used as a preliminary step in the thin foil preparation procedure for TEM to clearly mark the dislocation cell structure. TEM observations were then performed inside the dislocation cells only.