PULSED LASER ASSISTED EPITAXY OF GEXSI1-X ALLOYS ON SI(100)

The epitaxial quality of GexSi1-x films grown on Si<100> by a novel laser-assisted technique has been investigated for compositions in the range x less-than-or-equal-to 0.37 and thicknesses between 50 and 500 nm. Epitaxy is induced during electron beam deposition of GexSi1-x films on Si substrates by pulses of an excimer laser operating at 308 nm with 30 ns pulse duration. Good epitaxial growth is obtained for 50 nm films for x less-than-or-equal-to 0.04 on chemically cleaned Si(100) surfaces even in the presence of substantial fluorine coverage. Using a predeposition/crystallization of a 50 nm pure-Si buffer layer, good epitaxy is then obtained in 50 nm films for x = 0.05-0.13. At x = 0.07, defect-free alloys have been grown up to thicknesses of 0.5-mu-m. However, for films with compositions above 19 at.% Ge, dislocations at a nearly constant density of almost-equal-to 10-mu-m/mu-m2 are observed. This uniform density suggests a breakdown mechanism other than simple strain relaxation.