Interface Stability During Solid Phase Epitaxy of Strained Ge_xSi_1−x Films on Si(100)

Abstract

Strained solid phase epitaxial (SPE) regrowth of amorphous Ge_xSi_1−x on Si(100) substrates was studied using time-resolved reflectivity (TRR). Films of CVD-grown Ge_0.13Si_0.87 on Si were amorphized by Si ion implantation, and subsequently regrown at temperatures between 550°C and 610°C. Information on regrowth dynamics and interface roughness evolution was obtained by accurately modeling the complicated TRR data for Ge_xSi_1−x regrowth using a moving, statistically roughening interface. The SPE regrowth rate slowed as the interface crossed into the Ge_xSi_1−x layer and the originally planar interface roughened, as confirmed by transmission electron microscopy. A minimum in the regrowth velocity was observed after regrowing approximately 60 nm into the Ge_xSi_1−x layer; the SPE rate subsequently increased to a final, thickness-dependent velocity that was still below that for pure Si. Upon entering the Ge_xSi_1−x layer, the interface roughened quickly to a 15–20 nm amplitude, increasing only slightly more during the remainder of regrowth. The degree of roughening and velocity reduction was found to be dependent on the anneal temperature. In contrast, samples with low Ge concentrations (< 3 at. %) prepared by ion implantation exhibited minimal interface roughening and essentially identical SPE velocities as pure Si.