X-RAY-ABSORPTION STUDIES OF STRAIN IN EPITAXIAL (SI-GE) ATOMIC LAYER SUPERLATTICE AND ALLOY-FILMS

The Si 1s (K-shell) X-ray absorption spectra of a series of strained S ixGe100-x alloy thin films and several {(Si)(m)(Ge)(n)}(p) atomic laye r superlattices (ALS) grown epitaxially on Si(100) and Ge(100) substra tes have been investigated using plane polarized synchrotron radiation . Polarization dependent Components of the signal ale attributed to an isotropic states associated with strain-induced tetragonal distortions . The sense of the polarization is shown to be identical for all compo sitions (x = 25 to 92) of SiGe alloys grown on Si(100) substrates. The opposite polarization dependence is found to occur for all SixGe100-x alloys (x = 12 to 50) grown on Ge(100) substrates. The polarization d ependence and shape of the near edge spectral features of alloy and AL S samples which have similar (average) chemical composition are remark ably similar. A preliminary comparison of the alloy results with liter ature band structure calculations is made.