The shape of self-assembled InAs islands grown by molecular beam epitaxy

We have determined the shape of InAs quantum dots using reflection high energy electron diffraction. Our results indicate that self-assembled InAs islands possess a pyramidal shape with {136} bounding facets. This shape is characterized by C-2 upsilon symmetry and a parallelogram base, which is elongated along the [1(1) over bar 0] direction. Cross-sectional transmission electron microscopy images taken along the [110] and [1(1) over bar 0] directions as well as atomic force microscopy images strongly support the {136} shape. Furthermore, polarization-resolved photoluminescence spectra show-strong in-plane anisotropy, with emission predominantly polarized along the [1(1) over bar 0] direction, consistent with the proposed quantum dot shape.