SOLID-PHASE EPITAXIAL-GROWTH OF GE-SI ALLOYS MADE BY ION-IMPLANTATION

Solid-phase epitaxial growth was studied in germanium-implanted <100> silicon wafers as a function of germanium fluence, annealing temperature, and time. MeV He Rutherford backscattering in channeling conditions, cross-sectional transmission electron microscopy, double-crystal x-ray diffraction, and secondary-ion mass spectroscopy techniques were used to characterize the samples. At low fluences, up to 1 x 10(15) cm-2 at 130 keV, the crystallization kinetics is similar to that measured on self-amorphized silicon. In the high-dose samples, prepared by multiple implants with a total dose of 3.12 x 10(16) cm-2, the growth rate at fixed temperatures decreases. A comparison with literature data, obtained by similar experiments performed on amorphized uniform GexSi100-x films prepared by molecular-beam epitaxy or chemical-vapor deposition, reveals that the concentration gradient, unavoidable in implanted samples mainly at the end of the ion range region, is strictly connected with the observed decrease.