Pore formation on n-InP

Abstract

The present work deals with localized dissolution processes of n-type InP(100). Pore growth can be electrochemically initiated on the n-type material in the dark in HCl, HBr and HF solutions and leads after extended polarization to the formation of a porous InP structure. The porous structures were characterized by SEM, AES, and PL measurements. The pore morphology depends strongly on the electrochemical conditions and the type of halogen acid present in the electrolyte. AES depth profiles show that the composition of the porous layer is strongly affected by the electrolyte. For all electrolytes depletion of In was observed; this effect is the strongest for HBr and the weakest for HF. Uptake of electrolyte anions is the highest for HBr and lowest for HF. From scratch experiments it is clear that the pore initiation process is strongly influenced by surface defects. The morphology of the dissolution process also strongly depends on illumination as assessed by an experiment using a laser beam for a local surface illumination. At high illumination intensity, electropolishing instead of pore formation takes place. The finest pore structure was obtained in the dark. Structures formed in HF show visible photoluminescence in the yellow to red range of the spectrum, whereas for HCl and HBr treated samples no significant visible PL was obtained.