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 v symmetry and a parallelogram base, which is elongated along the [11̅0] direction. Cross-sectional transmission electron microscopy images taken along the [110] and [11̅0] 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 [11̅0] direction, consistent with the proposed quantum dot shape.