Thickness–composition diagrams of Stranski–Krastanov mode in the GaPSb/GaP and InGaAs/GaAs systems

Abstract The strain, surface, and interface energies of the GaPSb/GaP and InGaAs/GaAs systems were calculated for three kinds of pre-determined structure which represent the Frank–van der Merwe (FM), the Stranski–Krastanov (SK), and the Volmer–Weber (VW) modes of epitaxial growth. The free energy for each structure was estimated as a function of thickness and composition or lattice misfit. By comparison of the free energy of each mode, thickness–composition mode diagrams which express the stable region of each mode were determined for the GaPSb/GaP and InGaAs/GaAs(1 1 1) systems. It is found that all three growth modes appear in the mode diagram determined only by the calculation of the free energy. The SK mode appears only when the lattice misfit is large and the layer is thick. The VW mode appears only when the lattice misfit is large and the layer is thin. The SK mode appears in both systems, but the VW mode appears only in the GaPSb/GaP system. The stable region of the SK mode in the mode diagram is wider in the GaPSb/GaP system than that in the InGaAs/GaAs system because the strain energy of the GaPSb/GaP structure increases more strongly as the lattice misfit increases.