OBSERVATION OF THE 2D-3D GROWTH MODE TRANSITION IN THE INAS GAAS SYSTEM/

Self-organized InAs quantum dot structures were prepared by low pressu re metalorganic vapor phase epitaxy (MOVPE) using the Stranski-Krastan ow growth mode. We present photoluminescence (PL) and atomic force mic roscopy (AFM) studies of the transition from a 2D InAs wetting layer t o 3D quantum sized islands. The very narrow window where this transiti on takes place could be studied in detail by taking advantage of the s light growth rate gradient of our MOVPE system. After the growth of a critical layer thickness, first quantum dots occur. From the PL spectr a obtained at different positions on the wafer, we conclude that a par t of the wetting layer is consumed by the dot formation process. This is further confirmed by AFM measurements. Also a qualitative correlati on between dot density and PL intensity is described. Moreover, we obs erved that the dot formation can be suppressed by instantaneous overgr owth. Besides the overgrowth temperature the growth interruption betwe en the InAs film and the GaAs cap layer was found to be of great impor tance for the dot formation.