Evolution of Stress and Relaxation of Strain of Ge and SiGe Alloy Films on Si(001)

Abstract

AbstractWe report on real time stress measurements by a sensitive cantilever beam technique of Ge and SiGe Alloy Films on Si(001) in combination with structural investigations by in situ STM (scanning tunneling microscopy) and ex situ AFM (atomic force microscopy). Characteristic features in the stress curves provide detailed insight into the development and relief of the misfit strain as well as the respective growth mode. For the Stranski-Krastanow system Ge/Si(001) the strain relaxation proceeds mainly in two steps: (i) by the formation of 3D islands on top of the Ge wetting layer and (ii) via misfit dislocations in larger 3D islands and upon their percolation. Co-deposition of Si influences the stress behavior drastically. The growth mode changes from Stranski-Krastanow to a kinetic 3D island mode at Si concentrations of about 20% leading to the so far smallest quantum dots of the Ge/Si system.