Self-assembled In0.4Ga0.6As islands on GaAs (3 1 1)B substrates with AlxGa1-xAs buffer layers of different aluminum compositions have been grown by atomic hydrogen-assisted molecular beam epitaxy. It is found that the critical thickness decreases slightly with the addition of Al in the buffer layer, while the spatial alignment of the In0.4Ga0.6As islands deteriorates greatly from the well-defined two-dimensional lattice on the GaAs buffer. All these differences are related to the enhanced bond strength of At in the buffer by slowing the column III atom migration on the growing surface, and the reduced alloying effects between AlGaAs buffer and deposited InGaAs during growth. (C) 2002 Elsevier Science B.V. All rights reserved.