Pore growth on n-type InP(100) can be electrochemically initiated in HCl and HF solutions by polarizing the material anodic to a critical potential value-the pore formation potential (PFP). At surface defects however, the PFP is significantly lower (shifted cathodically). This is evident from simple scratch experiments as well as experiments using focused ion beam (FIB) implantation of Si2+ to write defined surface damage/implant patterns into n-type InP(100) substrates. These implant sites represent initiation sites for the onset of dissolution processes. Selective pore formation within the implant patterns is achieved if polarization of the n-type material is carried out anodic to the PFP corresponding to defects but cathodic to the PFP of the unimplanted surface. Furthermore, it is shown that the pore morphology depends strongly on the type of halogen acid present in the electrolyte. Scanning AES images show that the composition of the porous layers is strongly altered from the bulk composition. (C) 2003 Elsevier Science Ltd. All rights reserved.