TETRAGONAL LATTICE DISTORTION AND TENSILE-STRESS IN GAAS-LAYERS GROWN ON SI SUBSTRATES BY MOCVD

The lattice distortion and stress in GaAs layers grown on Si substrates by MOCVD have been studied. The lattice is tetragonally distorted under tensile stress at room temperature, contrary to the compressive stress expected from the fact that the lattice parameter of GaAs is greater than that of Si. The degree of lattice distortion and tensile stress is quantitatively explained by the purely elastic distortion due to the difference between the thermal expansion coefficients of GaAs and Si. This result demonstrates that the GaAs layer is stress-free at the higher growth temperature of the MOCVD two-step growth method and therefore thick GaAs layers can be grown on Si.