Thermodynamic mixing functions in CdTe dopant systems

The CdTe melt is a predominant associated solution (dissociation grade α=5% at melting point). The aim of the work was Ga, In, Tl impurities influence on a value investigation. In the framework of the regular solution model, interaction energy ω in CdTe-dopant solutions, thermodynamic mixing functions and CdTe dissociation grade in these solutions were calculated.Obtained results show predominant heteropartical interaction (negative ω values) in both CdTe-In and CdTe-Tl systems and homopartical (positive ω values) in the CdTe-Ga one. Analysis of calculated mixing functions witness, that the investigated solutions are intermediate between regular and athermal ones. Impurities essentially intensify CdTe dissociation. The most pronounced effect is caused by Tl and Ga (CdTe dissociation grade gain reaching 20-40% at different dopant concentrations). The obtained results can be used as initial during elaboration of CdTe single crystals growth technologies from solutions in liquid metals

Galvanomagnetic properties of CdTe below and above the melting point

Temperature dependence of conductivity � and Hall coefficient RH is measured by DC and AC methods at temperatures between 600-1180°C. Two experimental approaches are used. Galvanomagnetic measurements at defined temperature and Cd or Te pressure are performed in solid samples in the whole field of stability of solid in the pressure-temperature (P-T) diagram. Galvanomagnetic measurements define temperature both in solid and in liquid phase. The typical semiconducting character of � and 1/|eRH|, when both parameters increase with temperature, is observed also in the liquid. The negative sign of RH is observed above 600°C within the whole region of stability of solid, both at Cd and at Te saturation, and RH < 0 both in solid and liquid. 1/|eRH| reaches 5 � 1019 cm-3 at 1180°C and the corresponding Hall mobility is 20 cm2/Vs. Three slopes characterize the temperature dependence of a 0.7 eV in the solid CdTe below the melting point 1092°C and 4.6 eV in the liquid phase at 1092°C < T < 1160°C. Above 1160°C, conductivity increases moderately with the slope 0.8 eV. The experimental data for solid CdTe are evaluated by a theoretical model, including electrons from both the central minimum (�-point) and four satellite minima (L-point) of the Brillouin zone. The ab initio results fit our experimental data after small modifications very well