HRXRD studies of strain relaxation in ion-implanted strained Si on relaxed Si1−xGex

Abstract

The relaxation process of ion-implanted strained silicon films grown on silicon-rich relaxed Si1−xGex alloys was studied to determine the critical strain regime necessary for the breakdown of solid phase epitaxial recrystallization. Experimental structures were grown via molecular beam epitaxy (MBE) and contained a 50nm strained silicon capping layer on relaxed Si1−xGex. The relaxed Si1−xGex alloy compositions range from 0 to 30at.% germanium. A 12keV Si+ implant at a fluence of 1×1015atoms/cm2 was used to generate an amorphous layer ∼30nm thick, confining it to the strained silicon cap. The degree of relaxation of the silicon cap layer was quantified by high-resolution X-ray diffraction (HRXRD) omega–2theta rocking curves and reciprocal space maps. Maps were acquired for the (004) and (113) reflections to obtain the in and out-of-plane lattice parameter of the layers. Upon annealing, the solid phase regrowth (SPER) process broke down for the highest level of strain. Additionally, regrowth related defects were observed in these samples using cross-sectional transmission electron microscopy (XTEM). These results indicate a reduction of strain in the Si0.7Ge0.3 samples occur as a result of SPER breakdown that generated dislocations and stacking faults throughout the silicon capping layer.