A complex analysis of In-doped PbSnTe films has revealed their inhomog
eneity in structure and in composition as well. A more detailed explor
ation has shown that a spatial phase separation occurred during film f
ormation in the MBE process. Use of various surface science techniques
has permitted an investigation of the distribution of the elements on
the surface and in depth and this allowed us to find out the influenc
e of some growth process conditions on the properties of the films.