Shape and surface morphology changes during the initial stages of encapsulation of InAs/GaAs quantum dots

The change in shape and surface morphology of InAs/GaAs(0 0 1) quantum dots (QDs) during their initial encapsulation by GaAs has been studied using re flection high energy electron diffraction (RHEED) and scanning tunnelling m icroscopy (STM). The shape of the QDs changes significantly during the earl iest stages of overgrowth. In situ RHEED measurements show a significant ch evron angle change after deposition of only 2 ML of GaAs, before losing all crystallographic structure as more GaAs is deposited. STM results indicate significant surface mass transport, the height of the QDs decreases faster than the rate at which the GaAs capping layer is deposited and the QDs eff ectively "collapse" during the earliest stages of encapsulation. The area o f the partially capped QDs increases significantly with increasing GaAs dep osition and there is an anistropic increase in shape with significant elong ation along the [1 1 0] azimuth. (C) 2001 Elsevier Science B.V. All rights reserved.