Thermodynamic Analysis of Phase stability of Thin Film in III-V Alloy

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Effect of elastic strain on the phase equilibria of thin films in the III-V alloy semiconductor systems has been investigated. The Gibbs energies of liquid and compound phases are approximated by regular solution and sublattice models, respectively. The strain energy in estimated from the magnitude of misfit between the stress-free lattice parameters of film and substrate and the layer thickness of thin film where the misfit dislocations are introduced at the critical thickness when the strain energy density exceeds an energy barrier. The results obtained are as follows.(1) Growth of Ga (As, Sb) films on GaAs substrate :The miscibility gap of the epitaxial Ga (As, Sb) layer is shifted to the GaSb side due to the strain energy.(2) Growth of Ga (As, Sb) films on InP substrate :The homogeneous solid solution of GaAs_x Sb_<1-x> for x<approximately equal> 0.5 is predicted to be stable in the growth form the liquid phase epitaxy due to the lattice-matched GaAs_<0.51> Sb_<0.49> on InP substrate, though this composition is lying within the miscibility gap in bulk state.(3) Growth of (Ga, In) P films on GaP substrate :The summit temperature of miscibility gap in the (Ga, In) P compound is raised to higher temperature for the epitaxial layers.(4) In order to extend the present analysis to the II (Zn, Cd, Hg) and VI (S, Se, Te) alloy semiconductor systems, the miscibility gaps of ternary and quaternary bulk compounds are analyzed thermodynamically.