Planar InAs growth on GaAs(001) and subsequent quantum dot formation by a surface induced morphological instability

Abstract

InAs growth on GaAs has been studied extensively and most recently for the self-assembly of quantum dots on the surface. In this work, we have studied the growth conditions to form planar InAs, at an In beam-equivalent pressure of 3.1×10−8 Torr, under the metal rich (4×2) reconstruction and the subsequent formation of quantum dots (QDs) condensed from this layer by a rapid change in the As4 pressure. Atomic force microscopy (AFM) studied the surface morphology of InAs resulting from a nominal 12 ML growth with various As4 growth pressures while maintaining a metal rich condition. It was found that the surface roughness was dependent on the As4 pressure. At the higher As4 pressures studied, the growth was extremely rough and much smoother at the lower As4 pressures. For a beam-equivalent pressure of 1×10−7 Torr for As4 and 3.1×10−8 Torr for In, growth was seen to remain planar for a deposition thickness up to 3 ML. AFM analysis showed that a fingered morphology was formed with a roughness of ∼1 ML. When the As4 pressure incident on this surface was quickly changed, the reflection high-energy electron diffraction showed this surface roughened. Subsequent AFM analysis showed that QDs formed in long chains oriented down the [110]. We propose a model in which the fingered surface is segmented due to an underlying dislocation array in the formation of the chained QDs.