Distinctly different two-dimensional ordering alignments of InGaAs island arrays on GaAs(3 1 1)B and AlGaAs(3 1 1)B surfaces

By using the atomic force microscopy image, fast Fourier transformation and auto-correlation spectrum analysis, we have systematically investigated the spatial alignment of self-assembled In_0.4Ga_0.6As islands on the GaAs(3 1 1)B and the AlGaAs(3 1 1)B surfaces grown by atomic hydrogen assisted molecular beam epitaxy. Surprisingly, it is revealed that InGaAs island arrays are aligned in very different patterns on these two surfaces. They are aligned in a well-defined square two-dimensional (2D) lattice when formed on GaAs surface, but in a nearly perfect hexagonal 2D lattice when formed on AlGaAs surface, despite the fact that both AlGaAs and GaAs have the same lattice mismatch with InGaAs. This striking difference is preliminarily related to the enhanced bond strength of Al in surface, which not only changes the surface energy, but also slows down column III atom migration on the growing surface.