Analysis of thin-film solid solutions on single-crystal silicon by simulation of x-ray rocking curves: B-Si and Ge-Si binary alloys

Abstract

B-Si and Ge-Si thin-film solid solutions on silicon at different compositions are analyzed by multiple-crystal x-ray diffraction. Computer simulations of the rocking curves are made with a diffraction model which, for dilute alloys, does not differ from that commonly reported in the literature. For sufficiently high solute atomic fractions, modifications are introduced to the Fourier coefficients of the crystal polarizability and to the parameters depending on the lattice strain. In the B-Si case, the comparison between strain and carrier profiles resulting from the simulations and electrical measurements, respectively, gives information on the fraction of substitutional B, the presence of precipitates, and their coherent or incoherent nature. In the Ge-Si case, the solute fraction, its depth gradient, and the static atomic disorder in the alloy are determined by means of the modified diffraction model. In particular, the determination of the atomic displacements around the lattice points in fully strained thin-film Ge-Si alloys give results larger than those evaluated by Monte Carlo calculations for relaxed solid solutions.