InP surface properties under ICP plasma etching using mixtures of chlorides and hydrides

This study is specifically related to Cl2-based plasma etching of InP surfaces. The analyses are carried out as a function of plasma parameters such as the gas pressure, RF power and the percentage of the chlorine. X-ray photoelectron spectroscopy allowed to compare the surface kinetics of both the chlorine plasma and the more conventional CH4/H2 plasma mixture. For the first time, a P-rich surface is obtained with the Cl2-ICP conditions used, in contrast to the In-rich surface obtained with classical CH4/H2 plasmas. Atomic force microscopy indicates that the surface roughness of the etched InP depends on the percentage of the gas precursors (Cl2, CH4 and Ar) introduced in the reactor. Correlations between this roughness and the indium surface depletion in Cl2-based plasmas were observed. The Raman spectra confirm the increase in surface disorder on one hand and provide information on the changes in free carrier concentration on the other hand. Cathodo-luminescence spectra show the enhanced surface recombination velocity and the presence of deep level defects in the band gap induced by the etch process.