Journal of Physical Studies 24(1), Article 1602 [10 pages] (2020) DOI: https://doi.org/10.30970/jps.24.1602 SPINODAL DECOMPOSITION OF ELASTICALLY STRESSED PHASES AND COMPOSITION MODULATION EFFECT IN GacIn1-cP SOLID SOLUTIONS P. P. Moskvin1 , S. I. Skurativskyi1 , H. B. Zasik1 , T. Ye. Nedashkivska2  1Zhytomyr Polytechnic State University, Zhytomyr, 103, Chudnivska St., Zhytomyr, 10005, Ukraine, 2Zhytomyr Ivan Franko State University, Zhytomyr, 40, Velyka Berdychivska St., Zhytomyr, 10008, Ukraine e-mail: moskvinpavel56@gmail.com, skurserg@gmail.com Received 11 June 2019; in final form 14 December 2019; accepted 20 December 2019; published online 11 March 2020

The Cahn and Hilliard model concept is adapted for describing the spinodal decomposition of Ga$_c$In$_{1-c}$P solid solutions grown on a GaAs substrate. The elastic strain energy of a thin layer of a solid solution is calculated on the assumption that it is coherently conjugated with a massive GaAs substrate. The excess energy of mixing of the components in the solid phase is modeled in the framework of the simple solutions theory. The resulting differential equation describing the variations of the semiconductor solid solution composition under various conditions of its synthesis is solved by numerical and qualitative analysis methods. In particular, the thermodynamic conditions for the appearance of the oscillation regime during the relaxation of the supersaturated metastable state of the solid phase are found by analyzing the phase portrait of the obtained differential equation. It is shown that the appearance of such oscillations, i.e. of the composition modulation effect in the solid solution, is caused by the mutual transition of the excess thermodynamic energy of mixing of the unstable solid phase into the energy of elastic stresses of coherently conjugated layers after decompositions. The concentration profiles of the components in the obtained oscillatory process differ significantly from the harmonic ones. This is explained by the strong correlation between the parameters of the differential equation and the material composition. Moreover, the derived solutions are revealed in a vicinity of the resonance state, which is characterized by a significant increase in the oscillation amplitudes and, as a consequence, the manifestation of system’s nonlinearity. The results obtained concern the formation of concentration domains during the spinodal decomposition of a semiconductor solid phase. The results for the calculations of the oscillating process parameters are compared with the data on the composition modulation effect, which is experimentally observed in the growth of elastically strained Ga$_c$In$_{1-c}$P - GaAs heterostructures. The range of thermodynamic parameters of the growth system where the composition modulation effect in the of Ga$_c$In$_{1-c}$P solid solutions has to be observed is specified on the system’s temperature-composition phase diagram.

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