The effects of carbon incorporation during GSMBE of Si1−yCy and Si1−x−yGexCy: growth dynamics and segregation

Si1−yCy(0 0 1) and Si1−x−yGexCy(0 0 1) layers were grown using gas source molecular beam epitaxy (GSMBE) with three precursors; methylsilane (CH3SiH3), disilane (Si2H6) and germane (GeH4). The effect of carbon on growth was studied by observing the change in period of the intensity oscillations of reflection high energy electron diffraction (RHEED) during the formation of Si/Si1−yCy heterojunctions. Si1−x−yGexCy layer thickness (growth rate) changes were measured ex situ using X-ray diffraction (XRD). A decrease in growth rate was measured in the presence of carbon and evidence for carbon segregation was collected. Temperature programmed desorption (TPD) was used to study the limiting effect carbon has on H2 desorption and disilane adsorption. The flux dependence of the growth rate was modelled and compared to experiment to highlight the relative importance of the sticking probability of disilane to the hydrogen desorption rate constant. The growth rate decrease during Si1−yCy(0 0 1) growth compared to that of Si(0 0 1) was shown to be dominated by a decrease in the sticking probability of disilane.