Formation of three-dimensional islands in subcritical layer deposition in Stranski-Krastanow growth
V. Shchukin, N. Ledentsov, and S. Rouvimov
Accepted
A new method for the formation of three-dimensional (3D) strained islands in lattice-mismatched (B on A) heteroepitaxy is proposed. Once B forms a wetting layer (WL) of a subcritical thickness, material C is deposited that is lattice-matched to A and does not wet B. Then B and C phase separate forming local B-rich and C-rich domains on the surface. The thickness of B-rich domains thus exceeds locally that of the initial film of B, and 3D islands may form as it is demonstrated by modeled phase diagrams of the C/B/A system. We show that the growth of subcritical InAs/GaAs(100) film followed by the deposition of AlAs results i) in the formation of Al-rich and In-rich domains in the WL, confirmed by chemically-sensitive scanning transmission electron microscopy (STEM), and ii) in the stimulated onset of 3D islands, as evidenced both by high resolution TEM and by a significant red shift of the photoluminescence spectrum, in agreement with the proposed model. PACS 68.65.-k, 68.66.Hb, 81.16.-c, 81.16.Dn, 81.16.Rf