Sm R[xlnx 1 xln1 xEq

The enthalpy of mixing is obtained by summing the nearest neighbor bond energies:

where the interaction parameter, Q, is:

where N0 is Avogadro's number.

Phase-diagram calculations are based on the free energy of mixing:

where the values for AHM and A5M are provided by Eq 9 and 10.

The regular-solution model does not provide much physical insight into the bonding and mixing of semiconductor solutions. As an empirical model, however, it can be used to interpolate and extrapolate phase-diagram information from limited experimental data. The regular-solution model has been used to calculate the phase diagrams in binary, ternary, and quaternary semiconductor systems.

Phase diagrams of many multicomponent systems are available in the literature (Ref 50, 51, 52). Thermodynamic analyses of solid composition against vapor composition have been published for the systems GaAs1-xPx, InAs1-xPx, Ini_ xGaxAs (Ref 53), and for the quaternary Ga1.xInxAs1.J,PJ (Ref 54). Generally, good agreement between calculations and experimental results is obtained.

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