Ultraclean Etching Of Gaas By Hcl Gas And In Situ Overgrowth Of (Al)Gaas By Molecular Beam Epitaxy

Etching of GaAs by HCl gas has been systematically studied with emphasis on the quality of the heterointerfaces formed by the direct overgrowth of AlGaAs on the etched GaAs surfaces in an ultrahigh vacuum processing system. The interfaces were characterized by the transport properties of the two-dimensional electron gas (2DEG) and the photoluminescence from the quantum wells, both of which were formed at the interfaces. We show that the interfaces prepared by the etching and overgrowth at the molecular beam epitaxy-grown clean GaAs surfaces can be quite clean and almost damage-free so that high mobility 2DEG can be formed. We also report the properties of the interfaces prepared by the etching and overgrowth at the air-exposed GaAs surfaces, to show that the impurities adsorbed during the air exposure are efficiently removed and 2DEG can be formed at the interfaces. (C) 1998 American Institute of Physics.