Laser induced epitaxial regrowth of Si1-xGex/Si layers produced by Ge ion implantation

Abstract Si 1- x Ge x /Si crystalline films have been obtained via pulsed laser annealing of Ge-implanted silicon crystals. Si(100) samples implanted in random geometry with 150 keV 74 Ge ions at doses of 5 × 10 16 and 10 17 ions cm -2 (17 at% maximum concentration) have been irradiated in air either with a single pulse Q-switched ruby laser (λ = 694 nm) or with a single pulse XeCl excimer laser (λ = 308 nm) at energy densities ranging from 0.1 to 1.5 J/cm 2 . Even though the threshold for the onset of large epitaxial grain formation is different at the two laser wavelengths, at an energy density of about 1 J/cm 2 a full epitaxial regrowth of the amorphous layer is reached for both wavelengths. No residual damage is evidenced either at the surface nor at the initial a–c interface while no germanium loss is measured. In this situation the regrown crystalline films show a constant Ge concentration profile over a depth of the order of 100–150 nm, followed by a Ge diffusion tail into the bulk silicon which increases with laser fluences. For the samples implanted with 10 17 Ge/cm 2 the final composition of the films is Si 0.9 Ge 0.1 . Although the crystallization process proceeds from the liquid phase, RBS-channeling measurements indicate that the regrown layer is highly strained. In fact the average strain in the layer corresponds to more than 50% of the misfit calculated on the basis of the maximum Ge concentration. Characterization of the defects in the recrystallized layers and in the substrate has been performed by using ion dechanneling and TEM observations. No evidence of line defects or dislocation loops is given by both techniques.