Structural aspects of the growth of InAs islands on InP substrate

Several samples with InAs deposit from 1.2 to 4 monolayers (ML) have been grown on InP(001) by gas source molecular beam epitaxy and examined by photoluminescence, transmission electron microscopy and Raman spectroscopy. Coherent InAs islands due to the Stransky-Krastanov growth mode has been achieved above 1.5 ML. Two different island growth modes depending on the total InAs coverage have been identified. From 1.5 to 2 ML, the average island height is 7 nm, while above 2.5 ML it is only 3-4 nm. The island volume is also decreased by a Factor 5. Below 2 ML, the dots are randomly distributed, while above 2.5 ML there is a typical distance of 40 nm independent on the island density. The relationship between island size, island shape and island spatial distribution is discussed. The islands are more elastically relaxed in the first growth mode than in the second one. The existence of two growth modes is attributed to the major role of the substrate distortion in the elastic relaxation mechanism.