Poisson's ratio of AIAs

Abstract

In this work, we present a new approach to determining Poisson's ratio of AlAs. This approach requires the growth of a particular structure with a multiple quantum well (MQW) - 10X[500 angstroms GaAs/800 angstroms Al<SUB>x</SUB>Ga<SUB>1-x</SUB>As] followed by two single layers - 0.5 (mu) AlAs and 0.5 (mu) Al<SUB>x</SUB>Ga<SUB>1-x</SUB>As on a GaAs substrate. The x-ray rocking curves of the as-grown sample give the perpendicular lattice constants in the two single epilayers, and following chemical etching to remove the two single layers, x-ray diffraction measurement of the MQW is used to determine the Al fraction x. With this data, we obtain a value for Poisson's ratio of AlAs which is V<SUB>AlAs</SUB> equals 0.255 +/- 0.003 assuming Vegard's law and a linear variation of the Al<SUB>x</SUB>Ga<SUB>1-x</SUB>As lattice constant with x. However we obtain V<SUB>AlAs</SUB> equals 0.328 +/- 0.003 if, as proposed by Z. R. Wasilewski, a nonlinear relationship with the bowing parameter c equals 1.245 X 10<SUP>-3</SUP> is assumed. The value of 0.328 is in good agreement with most recent results obtained which do not assume Vegard's law. Our results therefore support the violation of Vegard's law in describing the relationship between the lattice constant of AlGaAs and its composition.