Effect of V/III ratio and PH3 annealing on InAs dots grown by MOVPE on InP(001) step-bunched surfaces

The self-organisation of InAs nanostructures grown by MOVPE on 0.2 degrees misoriented (0 0 1)InP substrates has been studied as a function of growth parameters. The surface morphology of thin layers has been observed by atomic force microscopy for nominal thicknesses of about 3 and 6ML. The InAs material was deposited at 500 degreesC with V/III flux ratios ranging from 50 to 240. We observed that InAs dots were self-aligned along the bunched steps of the surface forming strips of several micrometers length, regularly spaced every 3-4 terraces. The surface distribution of the strips could be varied with the growth conditions, i.e. V/III flux ratio. The influence of the cooling atmosphere was also studied for samples cooled down from 500 degreesC to 350 degreesC during 6 min under either arsine or phosphine Bur. This step has been found to largely determine the surface morphology of the InAs nanostructures. Under phosphine atmosphere, we will take into account the strong As --> P exchange which takes place, (C) 2001 Elsevier Science B.V. All rights reserved.