Microscopic study of the surfactant‐assisted Si, Ge epitaxial growth
The Sb‐assisted Si, Ge epitaxial growth processes have been studied using high resolution photoemission. It is found that the initially ordered Sb monolayer on the Si(100) and Ge(100) surfaces occupies the epitaxial sites and fully saturates the surface dangling bonds. This results in a reduction of the surface energy. During the growth process, the Sb atoms and the deposited Si, Ge atoms change their positions. Sb atoms segregate to the growth front to form a new ordered layer while leaving the uniform epitaxial Si, Ge layer behind.
Novel strain-induced defect in thin molecular-beam epitaxy layers.
We have studied the morphology of thin epitaxial Ge films on Si(001). By terminating the surface with a monolayer of As during growth, Ge is forced to grow layer by layer, instead of the preferred mode, which is layer by layer for three monolayers, followed by islanding. In layer-by-layer growth, there are no nucleation sites for misfit dislocations to accommodate the 4% lattice mismatch. Instead, we observe by high-resolution transmission electron microscopy a novel strain relief defect combining two \ensuremath{\Sigma}9 boundaries and a twin. An estimate of the defect energy compares favorably with the energy of equivalent misfit dislocations.
Kinetics of Antimony Doping in Silicon Molecular Beam Epitaxy
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.