STRAIN CHARACTERIZATION OF EPITAXIALLY-GROWN SUPERLATTICES BY RAMAN SPECTROSCOPY

摘要

We have summarised results on the influence of the misfit-induced bisotropic strain on the Raman 'frequency shifts of the optical phonons from the centre of the Brillouin zone in epitaxially grown super lattices. Useful formulas connecting stress and/or strain to the phonon-frequency shifts are derived for the case of nearly backward Raman scattering geometry from superlat-tices grown along the [001] and [111] crystallographic orientations. These were used for the analysis of published data in two cases of undercritical (a) ZnS/ZnTe and ZnS/ZnSe and (b) InSb/In_(1-x)Al_xSb super lattices, both grown along (001). In the first case acceptable agreement was found between the experimental results from the literature and the calculations based on the PDPs of ZnS. In the second case, it was shown that, although the general trends have been approached on the basis of the PDPs of InSb, further experimental examination with complimentary methods (X-ray diffraction, electron microscopy, etc.) is necessary in order to arrive, through a more detailed agreement, at definite conclusions concerning the state of strain and the dislocation formation within such structures.