Optical anisotropy of InAs submonolayer quantum wells in a (311) GaAs matrix

The in-plane optical anisotropy which comes from the heavy-hole and the light-hole transitions in InAs submonolayers inserted in a (311)-oriented GaAs matrix is studied by reflectance-difference spectroscopy (RDS). The steplike density of states obtained from RDS demonstrates that the ultrathin InAs layers should be regarded as two-dimensional quantum wells rather than isolated clusters, even for the sample with only 1/3-ML InAs. The degree of anisotropy is found to be independent of the layer coverage, and is within the intrinsic anisotropy of (311)-oriented ultrathin quantum wells, indicating that there is little structural or strain anisotropy in the InAs submonolayer grown on a (311) GaAs surface.