In situ cleaning of GaAs substrates with HCl gas and hydrogen mixture prior to MBE growth

Abstract

The effect of hydrogen chloride (HCl) gas and hydrogen mixture etching on GaAs surface cleaning prior to MBE growth was studied. The carrier depletion layer formed around the substrate epitaxial layer interface was reduced significantly by the gas etching. The carbon impurity concentration around the substrate epitaxial interface, measured by secondary ion mass spectroscopy (SIMS), also decreased one order of magnitude. Reduced carrier depletion and carbon impurity concentration were almost independent of the etching depth. We thus believe that the surface cleaning effect originates in the chemical reaction between the residual carbon contamination on the substrate and nascent active hydrogen produced by HCl gas decomposition. An atomically flat surface of the gas-etched GaAs substrate was observed using in situ reflection high energy electron diffraction (RHEED).