Elastic constants and Poisson ratio in the system AlAs–GaAs

Near infrared Brillouin scattering was used to determine all three elastic constants, and hence Poisson’s ratio ν=C12/(C11+C12) of epitaxial AlxGa1−xAs layers on GaAs. The AlxGa1−xAs layers were grown by metalorganic chemical vapor deposition and molecular beam epitaxy. We found evidence for a slight bowing in all elastic constants versus Al composition x. The elastic constants of AlAs were determined to be C11=119.9 GPa±1.2 GPa, C12=57.5 GPa±1.3 GPa, and C44=56.6 GPa±0.7 GPa. From x-ray measurements and the Poisson ratio ν=0.324±0.004 the relaxed (cubic) AlAs lattice constant is found to be aAlAs=5.661 72 ű0.000 08 Å.