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 temperatu re dependence which is due to desorption of one or both components fro m the growing surface. The measured desorption rate appears to be ther mally 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 ene rgy corresponding to a well-defined microscopic process. We argue that no weak-binding precursor state is needed for reproducing the experim ental growth rate of CdTe. Using Burton, Cabrera and Frank's theory an d by performing Monte Carlo simulations of a one-particle model for de position, diffusion, aggregation and desorption, we have found that th e macroscopic desorption rate appears to be thermally activated over a large range of temperatures. This rate is a combination of all the mi croscopic energies - diffusion barrier and desorption barrier - and it can take values of a few tenths of an electronvolt, even though all m icroscopic energies are much larger. A very simplified model of CdTe g rowth is thus proposed and tested against experimental measurements of growth rates for various temperatures and deposition fluxes (C) 1998 Elsevier Science B.V. All rights reserved.