STRESS VARIATION IN EPITAXIAL GAAS FILMS ON SILICON UNDER THERMAL-TREATMENT

High quality epitaxial GaAs films of 1.8 and 6.3 μm thickness on silicon substrates were examined for lattice distortion, misalignment and curvature by X-ray diffraction (Bond method) at 20-400 °C. These films were deposited by the metal-organic chemical vapour deposition method on the (001) plane of silicon using a buffer layer produced at Tb = 370 or 460 °C. A top layer was then grown at Tt = 560 or 650 °C. The GaAs films contract more strongly on cooling than the substrate, which causes a curvature and a tetragonal distortion below a critical temperature Tc. This temperature varies on thermal treatment at 200-400 °C and approaches Tb, the growth temperature of the buffer layer. The tetragonal distortion can be stabilized, so that Tc approximates Tb, if the GaAs films are annealed for several days at 400 °C. © 1990.