Low areal densities of InAs quantum dots on GaAs(1 0 0) prepared by molecular beam epitaxy

We report on a comparison of different In-deposition schemes to achieve low areal densities of self-assembled InAs quantum dots (QDs) on GaAs(1 0 0) via the Stranski-Krastanov growth mode employing solid source molecular beam epitaxy. We could realize densities in the range of 10⁷–10⁸ QDs/cm² utilizing homogeneous In-deposition and an annealing step. At least on 70% of a 3″ wafer the density was between 1 × 10⁷and 1 × 10⁸ QDs/cm². To achieve this, the In amount and the substrate temperature were controlled precisely. With inhomogeneous In-deposition via growing without sample rotation, we obtained low QD densities reproducible on a small fraction of the wafer surface. For a full-gradient, i.e., depositing the full In amount without rotation, the low-density area amounts in the best case to 10% of the overall wafer surface, whereas for a half-gradient, i.e. only half the In amount is deposited without rotation, it is 15%. The more In is deposited with substrate rotation, the less reproducible becomes the position of the low-density region on the wafer.