Dislocation loops in silicon-germanium alloys: The source of interstitials

The relationships between extended defect evolution and boron diffusion in Si0.77Ge0.23 have been investigated. A SiGe structure was grown by molecular beam epitaxy with a 3×1018atoms∕cm3 boron marker layer positioned 0.50μm below the surface. Samples were ion implanted with 60 keV Si+ at a dose of 1×1014atoms∕cm2 and subsequently annealed at 750 °C for various times. The evolution of extended defects in the near surface region was monitored with plan-view transmission electron microscopy. Secondary ion mass spectroscopy concentration profiles facilitated the characterization of boron diffusion. Boron experiences transient enhanced diffusion regulated by the dissolution of dislocation loops. The maximum diffusion enhancement in Si0.77Ge0.23 is less than that observed in pure Si.