Calculation of the Liquidus Isotherms and Component Activities in the Ga-As-Si and Ga-P-Si Ternary Systems

Abstract

Liquidus isotherms and thermodynamic activities have been calculated for the Ga‐As‐Si and Ga‐P‐Si ternary systems. The calculations are based on the assumption that the activities of the components in the liquid phase can be represented with sufficient accuracy by the ternary regular solution model. A least square analysis of the liquidus data for Si‐doped yields the three ternary interchange energies (i.c.e.'s). These are then used to construct the liquidus isotherms for Si‐doped , Ga‐ and As‐doped Si, and the ternary eutectic valley, all of which are in excellent agreement with the experimental results over a wide temperature and composition range. The ternary Ga‐As and Ga‐Si i.c.e.'s are in very good accord with the i.c.e.'s derived from the binary data but a similar test for the Si‐As i.c.e. shows a less satisfactory agreement. As the Ga‐P‐Si system has not yet been investigated, the calculations presented here are based solely on binary data and they need experimental confirmation. The implications of these results to crystal growth and the limitations of the regular solution model in the vicinity of the compound composition are also discussed.