Shape Transition of InAs Islands on InP (111)A

Atomic force microscopy (AFM) reveals that InAs islands grown on InP (111)A, as they grow in size, undergo a shape transition. Below a critical size of around 30 nm, round-shaped quantum dots form, while above this size they grow in the shape of triangles, reflecting the symmetry of the (111) substrates. The edges of triangular islands are aligned along the three equivalent {110} directions of the InP (111) surface. The triangular islands grow laterally much faster than vertically, indicating the aspect ratio decrease of the islands with increasing InAs coverage. Our results provide a better understanding of the self-organization behaviors of InAs on InP (111)A.