Dopant incorporation studies in silicon molecular beam epitaxy (Si MBE)

Abstract

We have studied dopant incorporation mechanisms in Si MBE via a model that allows for a steady state build-up of dopant on the host surface as a result of the incident flux, the desorbing flux and the incorporating rate. Application of this model to gallium on silicon will be discussed. Using isothermal desorption spectroscopy and Auger analysis we determine the activation energy for gallium desorption from silicon to be ∼2.88 eV. The activation energy for incorporation is deduced to be ∼1.20 eV. The time for achieving steady state conditions after abrupt changes in flux may be equivalent to several hundreds to a few thousands of angstroms of grown film at normal growth temperatures and rates. A technique has been developed by which the desired steady state value of the incorporated dopant is pre-adjusted so that the smear is reduced to negligible values (<200 Å). The saturation of the sticking coefficient at high fluxes has been measured.