In situ chemical etching of GaAs(001) and InP(001) substrates by gaseous HCl prior to molecular‐beam epitaxy growth

In situ chemical etching of GaAs (001) and InP (001) by gaseous HCl before molecular‐beam epitaxy (MBE) growth, on substrates previously etched with H2SO4/H2O2/H2O, has been studied by different surface and interface analysis techniques. Oxide free GaAs surfaces are obtained for low HCl pressures (p≥0.1 Torr) at 25 °C. The residual adsorbed chlorine is removed at 450 °C under vacuum or As4 pressure. In contrast to what is observed for GaAs, the surface oxide layer of InP substrates is not eliminated by gaseous HCl at room temperature. Capacitance–voltage measurements recorded after MBE growth on HCl gas deoxidized GaAs substrates do not detect any electrical perturbation of the substrate/layer interface, although the ion microprobe profiles show an increase in carboneous contamination of this interface. Moreover, the growth defect density is around four times lower when a deoxidation step by HCl gas is performed before the epitaxial growth of GaAs layers.