Strain field and related roughness formation in SiGe relaxed buffer layers

Strain distribution in SiGe heterostructures and its influence on the roughness formation of the overgrown structures were investigated. The crosshatch surface roughness was found to appear after the homoepitaxial regrowth of SiGe on the planarized SiGe buffer layers. The morphology of this roughness was almost equal to the in-plane strain distribution observed by Raman mapping measurement, which clearly demonstrated that the crosshatch roughness is formed by the strain distribution with the mechanism associated with the growth kinetics. Strain distribution wavelength was found to strongly depend on buffer thickness and strain fluctuation still existed on the very thick buffer layers. It can be said that the buffer thickness should be carefully taken into account for device applications. (c) 2005 Elsevier B.V. All rights reserved.