RAMAN-SCATTERING STUDY OF RESIDUAL STRAIN IN GAAS INP HETEROSTRUCTURES/

A Raman spectroscopy study on highly mismatched GaAs layers with thick ness ranging from 15 nm to 6.6 mum and grown by metal-organic vapor-ph ase epitaxy on InP (001) substrates, is reported. Both LO and TO GaAs phonons have been observed in backscattering and Brewster geometries. In the thinnest samples large frequency red shifts with respect to the bulk are measured indicating large residual tensile strains. The Rama n measurements agree with x-ray-diffraction measurements and confirm t hat layers thinner than 30 nm exhibit a 3D growth mechanism as suggest ed by transmission electron microscopy investigations.