Effect of atomic silicon and germanium beams on the growth kinetics of Si_{1 – x} Ge _x layers in Si–GeH₄ molecular beam epitaxy

Abstract

The steady-state kinetics of growth of Si_{1 – x} Ge _x layers in one version of hybrid molecular beam epitaxy with a molecular germane source and a sublimating silicon bar has been studied. It has been demonstrated that the processes of capture of hydride molecule radicals by the epitaxial surface and their subsequent decomposition must be taken into account in the analysis of growth kinetics. The comparison of experimental data with the results of kinetic analysis has revealed a close match between them. At low germane pressures ${P_{Ge{H_4}}}$ < 0.5 mTorr, the nature of the growth process is defined exclusively by the specifics of interaction between the molecular beam of Ge monohydride with the growth surface. The influence of the atomic Ge beam from the Si source only manifests at germane pressures exceeding 1 mTorr. Under these conditions, the fluxes of Ge and Si atoms from the sublimating Si source become equal, and the concentration of germyl molecules on the surface reaches saturation. The observed increase in the ${V_{Ge{H_3}}}$ parameter is associated with the activating influence of the flux of silicon atoms from the sublimating source on the decomposition of molecules.