Spontaneous composition modulation during Cd$_{x}$Hg$_{1-x}$Te(301) molecular beam epitaxy

The spontaneous composition modulation of a solid solution in Cd$_{x}$Hg$_{1-x}$Te during molecular beam epitaxy at CdTe/ZnTe/GaAs(301) substrates has been discovered. The study of the micromorphology of the film surfaces in an atomic-force microscope, together with the study of the film microstructure in a transmission electron microscope, has revealed that a periodic system of macrosteps oriented along the [010] direction and separated by (100) terraces is formed during epitaxial growth at temperatures higher than the optimal value on a Cd$_{x}$Hg$_{1-x}$Te(301) surface. The growth of the film of homogeneous composition is only possible at the fronts of macrosteps and it is not possible at (100) terraces, where a layered structure grows with composition modulated along the [100] direction having period of several tens of angstrцm. The observed phenomenon is explained by decreased adsorption of mercury atoms in the (100) plane.