Lattice deformation induced in surface GaAs layers by the selective lateral oxidation of buried AlxGa1-xAs layers was determined from the energy shift of the GaAs phonon line in Raman spectra excited with a focused laser beam. The procedure included a correction for the laser beam induced heating effects. The surface GaAs layer was found under small tensile stress in the oxidized regions of our samples with respect to the unoxidized regions. The deformation is 8×10-4 and is the same, within experimental error, for heterostructures incorporating pure AlAs layers or Al0.98Ga0.02As. Strong differences in Raman efficiency, as well as in photoluminescence efficiency, were observed for different samples, which are discussed in terms of the GaAs/oxide interface nonradiative recombination efficiency. © 1997 American Institute of Physics.