In situ x-ray topography measurement of the growth temperature dependence of the critical thickness of epitaxial InGaAs on GaAs

In situ high-resolution double-axis x-ray topography measurements have been made of the critical thickness at which misfit dislocations form in strained layers of In_xG_1-xAs grown epitaxially on (001) GaAs substrates. The critical thickness for formation of the initial fast B(g) misfit dislocations was found to be close to, but larger than the predictions of the Matthews-Blakeslee model. The discrepancy and the variation of the critical thickness with silicon doping have been modelled by inclusion of a Peierls stress in the force balance equation of misfit dislocation motion. Only a very small change was observed in the critical thickness as a function of growth temperature. Inclusion of a temperature-dependent term in the Matthews-Blakeslee model enabled an activation energy 0.3 ± 0.2 eV to be determined.