Elimination of Twinning in Molecular Beam Epitaxy of GaAs/Si and GaAs/Insulator

We present a study of GaAs nucleation on Si and (Ca, Sr) F2 (100) surfaces which shows that a 2D growth can be achieved for very thin (15 A°) deposits obtained at low temperature (25-100°C). Raising the temperature to 300-400°C leads to a stoichiometric and monocrystalline layer. Electron diffraction shows a diagram without twin spots and a surface devoid of noticeable roughness. The proposed procedure paves the way for the subsequent use of low temperature techniques aimed at the fabrication of co-integrated structures associating GaAs and Si.