Determination of sulphur in semiconductor-grade indium and indium phosphide by cathodic-stripping voltammetry

Abstract

A procedure is presented for the determination of sulphur in indium and indium phosphide within the range 0.01–100 p.p.m. by mass, based upon hydrogen sulphide evolution and differential-pulse cathodic-stripping voltammetry of the sulphide ion. Good recoveries of sulphide added to indium are demonstrated. Agreement with results obtained by spark-source mass spectrometry and reproducibilities at 0.1 and 1 p.p.m. levels by mass are satisfactory. Sulphur concentrations at the level of 100 p.p.m. by mass found in sulphur-doped indium phosphide are in agreement with the measured electrical carrier concentrations. Use of the procedure in establishing the sources of sulphur contamination in the liquid-phase epitaxial growth of indium phosphide layers is discussed briefly.