SEXAFS study of the GaAs/InP interface

Extended X-Ray Absorption Fine Structure measurements have been performed at the Ga and As K-edge of a nominal 3 ML GaAs grown by Molecular Beam Epitaxy on a InP(100) substrate deoxidized in As atmosphere. We exploited the in-plane linear polarization of the synchrotron radiation measuring SEXAFS spectra taken with the polarization vector parallel and perpendicular to the growth direction. By comparing the ratio of the coordination numbers of the pairs As-Ga As-In. Ga-As, taken at the two different angles of the polarization vector, a quantitative model of the interface is obtained. Two well defined layers form on the InP substrate giving rise to the following sample structure: 3 ML GaAs/3 Mt. InAs/lnP. This rules our the formation of InGaAs or InGaAsP layers at the interface.