Scanning tunneling microscopy study of GaAs overgrowth on InAs islands formed on GaAs[001]

Self-assembled InAs quantum dots by utilizing islanding in a Stranski-Krastanov mode are expected to have tremendous potential for electronic and optical applications. So far, shapes of InAs islands (dots) formed on GaAs[001] have been intensively examined with the use of reflection high-energy electron diffraction (RHEED), atomic force microscopy (AFM), scanning tunneling microscopy (STM), and cross-sectional STM. There are some discrepancies between STM and XSTM results, i.e., considerable differences in shape between before and after GaAs overgrowth on islands. In this paper, STM and RHEED have been used to investigate the overgrowth of GaAs capping layers on InAs islands formed on GaAs[001] substrates. In particular, we focus on how the overgrowth of GaAs on InAs islands proceeds and whether or not the overgrowth of GaAs brings about changes in the shape of InAs islands.