Deposition and growth with desorption for CdTe molecular beam epitaxy

It is well known that during epitaxial growth of thin films of almost all II-VI semiconductors, the growth rates show a pronounced temperature dependence which is due to desorption of one or both components from the growing surface. The measured desorption rate appears to be thermally activated with a strikingly small value: a few tenths of an eV. The explanation generally put forward is that the desorption of a weak-binding state acts as a "precursor" to chemisorption. According to this point of view, the small measured activation energy is a real energy corresponding to a well-defined microscopic process. We argue that no weak-binding precursor state is needed for reproducing the experimental growth rate of CdTe. Using Burton, Cabrera and Frank's theory and by performing Monte Carlo simulations of a one-particle model for deposition, diffusion, aggregation and desorption, we have found that the macroscopic desorption rate appears to be thermally activated over a large range of temperatures. This rate is a combination of all the microscopic energies - diffusion barrier and desorption barrier - and it can take values of a few tenths of an electronvolt, even though all microscopic energies are much larger. A very simplified model of CdTe growth is thus proposed and tested against experimental measurements of growth rates for various temperatures and deposition fluxes