Roughness in Si_1−xGe_x/Si superlattices: Growth temperature dependence

Structural measurements of buried interfaces utilizing x‐ray specular reflectivity profiles and diffuse scattering are discussed in this article. Evolution of roughness is kinetically limited at growth temperatures less than or equal to 400 °C. Then, the configuration of the growth surface is frozen, and leads to a vertical correlation of microroughness. For intermediate growth temperatures near 550 °C, the amplitude of roughness is minimized, since there is sufficient surface diffusion to smooth out short length scale roughness, but not enough for the surface to become unstable. Roughness reappears at higher growth temperatures, driven by strain in the SiGe layers, and the surface evolves on a time scale comparable to the layer growth, reducing the cross correlation between interfaces.