Ternary phase diagrams involving III-V alloys.
Creators: name: Gratton, Michel F.
Publisher: name: Université d'Ottawa / University of Ottawa
Year: 1978
Subjects: subject: Physics, Condensed Matter.

description: Ingots of GaAsySb1-y alloys have been prepared by various directional freezing techniques, the rate of freezing being kept sufficiently small (e.g. ∼ 0.5cm/day) that equilibrium conditions were obtained in cross-sectional slices. Samples from these slices have then been investigated by powder X-ray photographs and an X-ray fluorescence technique to determine the variation of lattice parameter with composition and the range of single phase solid solution. The results show that this system has a solid miscibility gap of maximum range 0.38 &lt; y &lt; 0.61 and that this corresponds to a peritectic reaction. In the range 0 &lt; y &lt; 0.38 the lattice parameter ao follows the Vegard line, but for 0.61 &lt; y &lt; 1.00 a o lies below this line. By annealing samples in the liquid-solid two-phase fields, data have also been obtained on the solidus curve and the peritectic temperature has been shown to be 745 +/- 5C. Solidus isotherms and isoconcentration lines have been experimentally determined for the Ga-In-Sb ternary diagram by means of the technique of annealing samples in the two-phase liquid-solid field and quenching, a method shown previously to give good results for the pseudobinary section. The results are compared with data predicted by the simple solution model. In this analysis, the linear temperature dependence of the interaction parameters alpha Ga-Sb, alphaIn-Sb, alphaGa-In and alpha GaSb-InSb has been examined and also the effect on the predicted data of variation in the values of these parameters. It is shown that while the model can give values of liquidus isotherms in good agreement with the available experimental data, the predicted solidus isotherms and isoconcentration lines are very different from the experimental data. No reasonable variation of the alpha parameters can eliminate this latter discrepancy and it is seen that in the case of this particular ternary system the simple solution model is of no value for prediction of solidus data. Tie-lines, boundaries of three-phase fields, range of immiscibility of the solid solutions, details of the liquidus sheet have been experimentally determined for the Ga-As-Sb ternary diagram again by means of the technique of annealing and quenching. Samples were annealed to equilibrium in either two-phase liquid-solid fields or three-phase liquid-solid-solid fields then quenched in order to freeze in the solid phase(s) in equilibrium in the solution. The results are compared with the predictions of the simple solution model which is successful in predicting a peritectic behaviour for the pseudobinary section of the diagram. The interaction parameters are treated as linearly dependent on temperature except for alphaGaAs-GaSb found to be constant. The model shows reasonable agreement with the few liquidus data available but fails to reproduce the measured range of the miscibility gap except at the peritectic temperature. No variation of the interaction parameters could bring the theoretical predictions in line with the experimental solidus data. The solid-solid interaction parameters were then tested for a dependence on solidus composition but this latter analysis showed that if any success is to be obtained here, those interaction parameters would have to depend on both the temperature and the solidus composition and in no simple manner.