DAMAGE AND STRAIN IN EPITAXIAL GEXSI1-X FILMS IRRADIATED WITH SI

The damage and strain induced by irradiation of both relaxed and pseud omorphic GexSi1-x films on Si(100) with 100 keV Si-28 ions at room tem perature have been studied by MeV He-4 channeling spectrometry and x-r ay double-crystal diffractometry. The ion energy was chosen to confine the major damage to the films. The results are compared with experime nts for room temperature Si irradiation of Si(100) and Ge(100). The ma ximum relative damage created in low-Ge content films studied here (x = 10%, 13%, 15%, 20%, and 22%) is considerably higher than the values obtained by interpolating between the results for relative damage in S i-irradiated single crystal Si and Ge. This, together with other facts , indicates that a relatively small fraction of Ge in Si has a signifi cant stabilizing effect on the retained damage generated by room-tempe rature irradiation with Si ions. The damage induced by irradiation pro duces positive perpendicular strain in GexSi1-x, which superimposes on the intrinsic positive perpendicular strain of the pseudomorphic or p artially relaxed films. In all of the cases studied here, the induced maximum perpendicular strain and the maximum relative damage initially increase slowly with the dose, but start to rise at an accelerated ra te above a threshold value of approximately 0.15% and 15%, respectivel y, until the samples are amorphized. The pre-existing pseudomorphic st rain in the GexSi1-x film does not significantly influence the maximum relative damage created by Si ion irradiation for all doses and x val ues. The relationship between the induced maximum perpendicular strain and the maximum relative damage differs from that found in bulk Si(10 0) and Ge(100).