Influence of the elastic energy due to lattice mismatch on phase equilibria in the epitaxy of As-Ga-In layers

Deviations in compositions are observed between phase equilibrium calculations and Liquid Phase Epitaxy (LPE) data of thin AsGayIn1− y layers grown on InP substrates. From the assessed thermodynamic properties of the ternary As-Ga-In, the influence of the strain energy due to lattice mismatch on epitaxial phase equilibria of thin layers is analysed. The classical formula for calculating the elastic energy due to tetragonal distortion is expressed into a Redlich-Kister form in order to perform the thermodynamic and phase equilibrium calculations using the Thermo-Calc software. The calculated results for liquidus and liquid-solid partition of In (or Ga) in the As-Ga-In system at 920 K that should be grown on InP(111) and InP(100) substrates agree well with the experimental LPE data. These results confirm the importance of the strain energy for thin epitaxial layers. A database was developed for this system in which the elastic energy parameters are included. The pseudobinary GaAs-InAs diagram, isothermal sections and equilibrium partial pressures in relation with maximum congruent vaporisation temperature, are calculated with this database and are compared with those calculated without considering the elastic energy.