Measurement of the surface strain induced by reconstructed surfaces of GaAs(001) using photoreflectance and reflectance-difference spectroscopies

We report photoreflectance-difference and reflectance-difference measurements on reconstructed GaAs (001) surfaces. From these data the linear and quadratic electro-optic coefficient spectra are determined in the important 2.8-3.4 eV spectral region. The surface strain and fields induced by the surface reconstruction are also determined. We show experimentally that between c(4x4) and (2x4) surfaces, there is an inversion of the surface electric field which we attribute to a direct piezo-electric effect related to the surface strain induced by reconstruction