Determination of Ga interdiffusion in InAs : GaAs(001) islands by x-ray reciprocal space mapping

Abstract

Structural and chemical properties of self-assembled InAs islands grown on GaAs(001) were studied using x-ray scattering. Two measurements performed under grazing incidence geometry were correlated to obtain the three-dimensional strain and chemical status of InGaAs coherent islands. Grazing incidence diffraction was employed to reveal the in-plane strain-size interplay. Mapping out the reciprocal space near the GaAs(022) reflection and correlating the in-plane and out-of-plane strain information, we have been able to quantify the tetragonal distortion of the unit cells at any position inside the islands. Simple theory of elasticity of alloys enabled us to analyse the elastic deformation of the unit cells. Any variation in the expected tetragonal distortion of the unit cell was associated to the presence of Ga atoms inside the islands. Using this method, the Ga content in our islands was shown to vary linearly from 25% (island bottom) to 8% (island top).