Non-stoichiometry and properties of ternary semiconductor phases of variable composition based on IV–VI compounds

An overview and analysis of our experimental data on the crystal structure, mechanical, thermal, galvanomagnetic and thermoelectric properties vs composition of the ternary semiconductor phases based on IV–Te compounds in the IV–X–Te systems (IV–Ge, Sn, Pb; X–Cu, Ag, Cd, In, Ga, Bi, Sb, Mn, V) are given. The separate and joint effect of deviation from stoichiometry and cation substitution on the IV–X–Te phase properties is established using the method of ‘controlled atomic defects’. Some general regularities and new physical phenomena connected with simultaneous presence of intrinsic and impurity point defects are detected. The influence of the cation substitution on the intrinsic defect equilibrium is established. It is shown that critical phenomena of percolation nature are observed in the range of small impurity contents as well as small intrinsic defect concentrations. Principally new models of the energy band structure of IV–X–Te ternary phases, which take into consideration a high concentration of non-stoichiometric defects, are proposed. The role of long- and short-range ordering is discussed. The formation of complexes as a result of chemical interaction between impurity and host atoms is detected. The above-mentioned phenomena are common for ternary phases and should be taken into account when developing materials for different applications.