Investigation of GaAs/Si material by x-ray double-crystal diffraction

Abstract

GaAs epilayer films on Si substrates grown by molecular-beam epitaxy were investigated by the x-ray double-crystal diffraction method. The rocking curves were recorded for different diffraction vectors of samples. The results show that the unit-cell volumes of GaAs epilayers are smaller than that of the GaAs bulk material. The strained-layer superlattice buffer layer can improve the quality of the film, especially in the surface lamella. The parameter W′ = Wexpt/(√‖γh‖/γ0/sin 2θB) is introduced to describe the quality of different depths of epilayers. As the x-ray incident angle is increased, W′ also increases, that is, the quality of the film deteriorates with increasing penetration distance of the x-ray beam. Therefore, W′ can be considered as a parameter that describes the degree of perfection of the epilayer along the depth below the surface. The cross-section transmission electron microscopy observations agree with the results of x-ray double-crystal diffraction.