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

摘要

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 x 10(-8) Torr, under the metal rich (4x2) reconstruction and the subsequent formation of quantum dots (QDs) condensed from this layer by a rapid change in the As-4 pressure. Atomic force microscopy (AFM) studied the surface morphology of InAs resulting from a nominal 12 ML growth with various As-4 growth pressures while maintaining a metal rich condition. It was found that the surface roughness was dependent on the As-4 pressure. At the higher As-4 pressures studied, the growth was extremely rough and much smoother at the lower As-4 pressures. For a beam-equivalent pressure of 1 x 10(-7) Torr for As-4 and 3.1 x 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 similar to1 ML. When the As-4 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.