In situ observation of low temperature growth of Ge on Si(1 1 1) by reflection high energy electron diffraction

Abstract

In this paper we investigate the initial stages of epitaxial growth of Ge on Si(111) and the impact of growth temperature on strain evolution in situ by reflection high energy electron diffraction (RHEED) for temperatures between 200°C and 400°C. The change in surface morphology from a flat wetting layer to subsequent islanding that is characteristic for Stranski–Krastanov growth is monitored by spot intensity analysis. The corresponding critical layer thickness is determined to 3.1<dc<3.4ML. In situ monitoring of the strain relaxation process reveals a contribution of the Si(111) 7×7-surface reconstruction to the strain relaxation process. High resolution transmission electron microscopy confirms that the Ge islands exhibit a high degree of structural perfection and an ordered interfacial misfit dislocation network already at a growth temperature of 200°C is established. The temperature dependency of island shape, density and height is characterized by atomic force microscopy and compared to the RHEED investigations.