COMPOSITION AND STRUCTURE OF SI-GE LAYERS PRODUCED BY ION-IMPLANTATION AND LASER MELTING

Si samples (001) oriented have been implanted with 10(17) Ge-74/cm2 (17.7 at.% maximum Ge concentration) and then pulse annealed with either ruby or excimer (XeCl) lasers in the energy density range from 0.1 to 1.5 J/cm2. Compositional and structural characterization has been performed showing that for both laser wavelengths the final product of the annealing process is a single crystal characterized by a surface layer about 150 nm thick whose composition is Si0.9Ge0.1. While after ruby laser irradiations defects are present even in the fully recrystallized samples, after XeCl irradiations good strained layers in epitaxy to the underlying silicon crystals and free from misfit dislocations are produced. Structural characterization of the regrown films indicates that the governing factor for the recovery of the crystalline quality and for the "building up of strain" is the state of the implantation "end-of-range defect" layer. When this defected layer is not melted, textured columnar grains are formed. Upon melting of the end-of-range defect layer, a single crystal epitaxial layer under compressive strain is formed.