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The present work deals with anodization processes of p-type InP(100) in different halogenic acids. The morphology of the attack depends strongly on the electrochemical conditions and the type of anion present in the electrolyte. Only electropolishing was observed in HCl while the formation of a porous oxide layer was obtained in HF. In HBr, however, pore growth into the bulk material can be achieved.

Localized pore formation on n-InP(100) surfaces under anodic polarization in 1M HCl were created and controlled by a two steps approach. First, scratches in the nanometer scale have been applied mechanically, using a Nano-Indenter. These scratches represent activated sites for pore growth due to their lowered electrochemical pore formation potential (U b d , a c t i v a t e d ), which is significantly cathodic to the formation potential on intact surfaces U b d (U b d , i n t a c t ). Thus, a potential window can be defined between U b d , a c t i v a t e d and U b d , i n t a c t , where anodic polarization in 1M HCl leads to selective pore formation follows, at a potential that is inside those window. Characterization by scanning electron microscopy shows that pore formation occurs only at the activated sites. Furthermore, both broadening and morphology of the pores depend strongly on the force load during the scratching process. Analysis of the scratched surface has been carried out before and after etching, using atomic force microscopy (AFM). The results clearly show that the porous region is significantly wider than the originally scratched region - this can be ascribed to dislocation formation in the vicinity of the scratch.

Selective pore formation can be electrochemically initiated on n-type InP(100) on presensitized surfaces. To create this presensitization, defect patterns were written into the surface by focused ion beam (FIB) implantation of Si ++ . These implant sites represent initiation sites for pore growth or for selective material dissolution in the patterns, if anodic polarization is carried out positive to the pore formation potential (PFP) of the defective surface but cathodic to the PFP of the intact surface. A variety of internal and external factors were found to influence the selectivity of the process. Parameters that significantly affect the morphology are polarization voltage, implantation dosage, the time and the anion present in the electrolyte. In the present work it is shown, that pore formation in 1 M HF only occurs for a small potential range and a certain dosage range of the implanted Si ++ ions. At other potentials or dosages, a homogenous dissolution of the implanted patterns takes place. Apart from direct selective porosification of InP surfaces, the process described can be used for a selective surface patterning.

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 Si 2+ 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.

Nanometer sized pores were formed for the first time on p-type InP surfaces by electrochemical anodic polarization in HF and HBr solutions in the dark. The surface structures were characterized with scanning electron microscopy (SEM), Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), and photo-luminescence (PL) measurements. It is found that the surface morphology strongly depends on the type of halogen acid present in the electrolyte, and that the anodized samples emit photoluminescence in the visible wavelength range.