Minimizing interface contamination in MBE overgrowth

Surface cleaning procedures including atomic hydrogen-assisted oxide desorp tion, ozone stripping and reevaporation for overgrowth on GaAs and AlxGa1-x As are studied by secondary ion mass spectrometry, capacitance/voltage prof iling and atomic force microscopy. On the GaAs surface an atomic hydrogen-a ssisted oxide removal drastically reduces the carbon contamination at the i nterface compared to thermal oxide desorption. On AlxGa1-xAs surfaces an ad ditional ozone treatment and dip in sulfuric acid is necessary to obtain sp ecular surfaces after regrowth. However, the carrier depletion at the inter face 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 reser ved.