Electrochemical etching of indium phosphide surfaces studied by voltammetry and scanned probe microscopes

Using voltammetry, X-ray photoemission spectroscopy (XPS), in situ electroc hemical scanning tunneling microscopy (STM), ex situ atomic force microscop y (AFM) and scanning electron microscope (SEM) measurements, electrochemica l etching modes for n-InP surfaces were investigated and optimized for unif orm and controlled etching in an HCl electrolyte. The voltammograms indicat ed the presence of active and passive regions. The surfaces obtained in the active region were clean and featureless with an rms roughness of 1.8 nm. On the other hand, the oxide cove:red surfaces obtained in the passive regi on were nonuniform and porous. Etching characteristics of the d.c. photo-an odic mode and the pulsed avalanche mode were then investigated and compared . Both modes were found to be highly controllable and produced uniform and clean surfaces, consuming eight holes per molecule of InP. In particular, t he pulsed avalanche etching mode realized an extremely high etch depth cont rollability of 3 x 10(-5) nm/pulse.