ELASTIC BEHAVIOR OF SI GE SUPERLATTICES DETERMINED BY BRILLOUIN LIGHT-SCATTERING/

The elastic properties of Si/Ge strained-layer superlattices have been studied by means of Brillouin light scattering spectroscopy. The supe rstructures, grown along the [001] direction, have composition modulat ion wavelengths ranging from 1.4 to 5.6 nm and Si/Ge ratios: 1:1, 3:1, 4:1 and 1:4. The study has been carried out in three different stages : (i) the checking of the non-influence from the substrate on the dete rmination of the elastic properties; (ii) the angular dependence of th e surface sound velocity within the surface plane; and (iii) the varia tion of the surface sound velocity with the modulation wavelength. The obtained data of hypersonic surface waves are in good agreement with those calculated from previous results reported in Si and Ge pure sing le-crystals. No evidence of anomalous supermodulus effect has been fou nd in these superlattices. (C) 1998 Elsevier Science S.A.