  The mechanisms controlling the growth rate and composition of epitaxial CdTe
and CdZnTe films were studied. The films were grown by isothermal closed space
configuration technique. A GaAs 100 substrate was exposed sequentially to the
elemental sources, Zn, Te, and Cd, in isothermal conditions. While growth of
ZnTe followed an atomic layer epitaxy, ALE, regime self regulated at one
monolayer per cycle; the CdTe films revealed different growth rates in
dependence of the growth parameters,exposure and purge times. Combination of
short purge times and larger Cd exposure times led to not self regulated growth
regime for CdTe. This is ascribed to large Cd coverages that were dependent on
Cd exposure times, following a Brunauer-Emmett and Teller-type adsorption.
However, for longer purge times and or short Cd exposure times, an ALE self
regulated regime was achieved with 2 ML per cycle. In this sense, the
self-regulation of the growth is limited by desorption, instead of absorption,
as in the traditional growth technique. Cd atoms substitution by Zn atoms and
subsequent evaporation of surface Cd atoms during Zn exposure has been proved.
The influence of these facts on the growth and composition of the alloy is
discussed.
