  Graded composition CdxZn1-xTe films were prepared by growing several
alternate layers of CdTe and ZnTe by the Isothermal Close Space Sublimation
technique. The thickness of both kinds of layers was modified along the
structure to produce an increase of the average concentration of CdTe towards
the surface of the films. Due to Zn/Cd inter-diffusion during the growth
process the sequence of layers was converted into a relatively smooth graded
composition film. According to X- ray diffraction characterization the layers
grew coherently with the (100) oriented GaAs substrates although they showed a
relatively high mosaicity. Theta-2theta plots show very wide diffraction peaks
as expected from variable composition samples. The band gap grading effect in
light absorption was also verified through transmission measurements, using
transparent substrates. Graded composition profiles of the thin films were
confirmed by x-ray photoelectron and secondary ion mass spectroscopies.
Moreover, quantitative Cd, Zn and Te profiles were obtained by the analysis of
Rutherford backscattering spectra of the samples. This analysis showed a CdTe
molar fraction profile ranging from approximately x = 0.8 at the surface of the
sample and x = 0.35 at the interface with the substrate. The possibility of
growing graded composition layers using a simple and cost-effective procedure
was demonstrated. This could be interesting in technological applications like
CdxZn1-xTe layers of variable composition in CdS/CdTe solar cells
