Low areal densities of InAs quantum dots on GaAs(100) 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(100) via the Stranski-Krastanov growth mode employing solid source molecular beam epitaxy. We could realize densities in the range of 10(7)-10(8) QDs/cm(2) utilizing homogeneous In deposition and an annealing step. At least on 70% of a 3 '' wafer the density was between 1 x 10(7 )and 1 x 10(8) QDs/cm(2). 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.