Relaxation of strained silicon on Si<inf>0.5</inf>Ge<inf>0.5</inf> virtual substrates

Abstract

Strain relaxation has been studied in tensile strained silicon layers grown on Si 0.5 Ge 0.5 virtual substrates, for layers many times the critical thickness, using high resolution x-ray diffraction. Layers up to 30 nm thick were found to relax less than 2% by the glide of preexisting 60°d islocations. Relaxation is limited because many of these dislocations dissociate into extended stacking faults that impede the dislocation glide. For thicker layers, nucleated microtwins were observed, which significantly increased relaxation to 14%. All these tensile strained layers are found to be much more stable than layers with comparable compressive strain.