Direct observation of the transition from a 2D layer to 3D islands at the initial stage of InGaAs growth on GaAs by AFM

We have studied the transition from two-dimensional (2D) growth to three-dimensional (3D) growth at the initial stage of In0.8Ga0.2As growth with the Stranski-Krastanov mode on GaAs by metal organic chemical vapor phase epitaxy. The surface morphology was observed by atomic force microscopy. In the early stage of the growth, the formation of 2D islands and that of holes were alternately repeated. 3D islands (quantum dots) appeared after the deposition of 3 monolayers. 2D islands with 4 monolayer thickness of In0.8Ga0.2As were also formed at the same time. The 2D islands shunned the quantum dots and grew laterally. In addition, we obtained a photoluminescence spectrum with several peaks corresponding to higher subbands with a high excitation intensity from the quantum dots.