Strain-induced material intermixing of InAs quantum dots in GaAs

A systematic investigation of the stacking behavior of InAs quantum dots (Q Ds) with varying GaAs interlayer thickness d is presented. We compare two-f old stacks of large QDs (approximate to 25 nm base width), which emit at 1. 30 mu m, to small QDs (approximate to 20 nm base width) emitting at 1.14 mu m. For large islands photoluminescence yields an energetic blueshift of th e second layer islands with decreasing d, although transmission electron mi croscopy clearly reveals a approximate to 70% larger dot size in the second layer, whereas for small islands a similar size increase of the dots in th e upper layer and an energetic redshift are observed. A detailed analysis o f confinement and material intermixing effects suggests that for large QDs strain driven material intermixing is dominant. For small QDs the confineme nt effect plays the major role and causes the observed photoluminescence en ergy redshifts. (C) 2000 American Institute of Physics. [S0003-6951(00)0193 8-0].