Influence of kinetic roughening on the epitaxial growth of silicon

The low temperature homoepitaxial growth of silicon has been probed in situ by Reflection High Energy Electron Diffraction (RHEED) in a Molecular Beam Epitaxy (MBE) chamber in the temperature range 250 o C-400 o C. The continuous change in the RHEED patterns during the growth of thick films (several hundred angstroms) shows the progressive appearance of a surface roughness during and after the decay of RHEED oscillations. This is a clear evidence for kinetic roughening in the case of silicon epitaxial growth at low temperatures on the Si(111) face. The surface width, σ, measured as the film thickness, h, is increased, can be described by: σ(h, T)∼Ah exp(E f /kT) with E f ∼0.65 eV. This is in marked difference with the kinetic roughening behavior measured during the growth of a metal like iron by means of the same RHEED technique (see Chevrier et al., Europhys. Lett. 8 (1991) 737). Furthermore, an extrapolation of this behavior to epitaxial growths at higher temperatures (T∼600 o C-800 o C) suggests an effective influence of kinetic roughening in the determination of growth temperatures generally used for silicon MBE (i.e. the empirical usual growth temperatures Tepi ∼ 650 o C). During growth at substrate temperatures between 250 o C and 400 o C, the nucleation of misoriented silicon islands takes place following the occurrence of kinetic roughening at the surface. In this range of temperatures, this suggests that the loss of epitaxy occurs on a rough surface through the proliferation of defects and of misoriented crystals