Surface Corrugation of GaAs Layers Grown on (775)B-Oriented GaAs Substrates by Molecular Beam Epitaxy

Surface morphologies of GaAs layers grown on (775)B-oriented GaAs substrates by molecular beam epitaxy were studied using atomic force microscopy. The surface of a GaAs layer grown on a (775)B GaAs substrate is flat when it is grown at a substrate temperature (T s) below 580°C, but corrugates regularly for T s ≥640°C. Similar periodic corrugation of the (775)B GaAs surface formed during thermal annealing at T s=640°C under As4 atmosphere (10-6 Torr), which is similar in shape to that of a GaAs layer in the early stage of growth (a GaAs layer thinner than 5 nm). As the thickness of a GaAs layer increases from 5 nm, the lateral period and step height of the corrugation increase and tend to saturate for thick GaAs layers (200 nm thick or more). The precise structure of the surface corrugation of a 3-nm-thick GaAs layer (the lateral period of 12 nm and step height of 1.2 nm) was observed as a corrugated AlAs-on-GaAs interface of a GaAs/(GaAs)5(AlAs)5 quantum well structure with an average well width of 3 nm by cross-sectional transmission electron microscopy observation.