Crystallographic properties of some ternary and multinary Te-based semiconductors

Abstract

Crystallographic properties of several single crystals of ternary ABC 2 ( A = Cu, Ag; B = In, Ga; C = Te, Se) compounds, of Cd 1− x Mn x Te (0.5 ≤ x ≤ 0.66), of quaternary and pentenary (CuIn 1− x Ga x Se 2(1− y Te 2 y with x = 0, 0.7, 1 and y = 0.135, 0.65, 0.4) solid solutions have been determined by single crystal X-ray diffraction. Many chalcopyrite compounds and alloys show thermal polymorphism involving order-disorder phase transitions, and the structure changes are characterized by a first order transition from ordered tetragonal chalcopyrite to the completely disordered zinc-blende and/or wurtzite structures. All the single crystals were grown by chemical vapour phase transport in a close tube using iodine as the transport agent. The phases observed in growing ternary compounds depend on the temperature used during the growth process. For the multinary solid solutions the situation appears to be more complex: in fact, together with the expected phases some altogether unexpected ones were detected, confirming the idea that the growth process of these compounds is dependent not only on temperature but also on parameters involving the composition and growth kinetics.