A layer of HgCdTe (15) epitaxially grown onto a crystalline support (10), e.g., of sapphire of GaAs. A CdTe substrate (5) is epitaxially grown to a thickness of between 1 micron and 5 microns on the support (10). A HgTe source (3) is spaced from the CdTe substrate (5) a distance of between 0.1 mm and 10 mm. The substrate (5) and source (3) are heated together in a thermally insulating, reusable ampoule (17) within a growth temperature range of between 500.degree. C. and 625.degree. C. for a growth step having a duration of between 5 minutes and 4 hours. Then an interdiffusion step is performed, in which the source (3) and substrate (5) are cooled within a temperature range of between 400.degree. C. and 500.degree. C. for a time of between 1 hour and 16 hours. In a first growth step embodiment, the source (3) and substrate (5) are isothermal. In a second growth step embodiment, the source (3) and substrate (5) are non-isothermal. Means are disclosed for preventing contamination of the reactants during HgTe (3) synthesis, and for polishing the HgCdTe layer (15).