Kinetics of Antimony Doping in Silicon Molecular Beam Epitaxy

Abstract

A new kinetic model for Sb doping into the Si MBE layer is proposed. In this model, Sb doping steps are assumed as follows: a fraction of impinging Sb₄ molecules adsorbs on the growing Si surface (adlayer) and monoatomic Sb desorbs from the adlayer into vapor; a fraction of monoatomic Sb in the adlayer is incorporated into the bulk, so that surface-concentration of Sb atoms may be in equilibrium with bulk-concentration of Sb. According to this model, calculated results successfully represent the present experimental data on relations between incident Sb₄ flux, Sb concentration in the adlayer and that in bulk. As a result, it is indicated that doping levels in MBE layers are uniquely determined by Sb concentration in the adlayer, and not by Sb₄ flux/Si flux ratio, when Si growth rate is lower than 1 Å/s.