Minimizing interface contamination in MBE overgrowth

Surface cleaning procedures including atomic hydrogen-assisted oxide desorption, ozone stripping and reevaporation for overgrowth on GaAs and AlxGa1-xAs are studied by secondary ion mass spectrometry, capacitance/voltage profiling and atomic force microscopy. On the GaAs surface an atomic hydrogen-assisted oxide removal drastically reduces the carbon contamination at the interface compared to thermal oxide desorption. On AlxGa1-xAs surfaces an additional ozone treatment and dip in sulfuric acid is necessary to obtain specular surfaces after regrowth. However, the carrier depletion at the interface is still large in this case. The oxygen based contamination on AlxGa1-xAs and, hence the charge depletion is efficiently reduced by reevaporation of a sacrificial GaAs cap. (C) 1999 Elsevier Science B.V. All rights reserved.