IV. Analysis of the experimental data found in the literature

The analysis of the literature data is complicated by the fact that different authors have used different combinations of molecular forms of V group elements. Therefore, the model was modified taking into account the molecular form of arsenic and phosphorus. For example, in [8] layers of solid GaP_xAs_1 - x solutions were grown from fluxes of As₄ and P₄ molecules. We used the monomolecular chemical adsorption pattern for As₄ and P₄ molecules. Activation energies for desorption of As₄ и P₄ were taken from [9]. Other parameters were adjusted on the basis of the experimental data [8]. Satisfactory matching between the experimental data and the model in the considered case was achieved only when we took into account that [8] used such epitaxy conditions, at which structure (3×6) should be observed with growth of GaAs and Ga-stabilized structure (2×4) should be observed with growth of GaP. The found model parameters were used for analysis of the data from other authors. Fig. 4 presents model and experimental phosphorus fractions in the layers generated in [8]. It follows from the data presented in the Figure that the model supposes that there is a range of growth conditions, within which phosphorus fraction in the solid solution decreases with growth of TS.

Fig. 4. Dependence of phosphorus fraction in solid GaP_xAs_1 – x solution on substrate temperature, at different relations of equivalent pressures in fluxes of As₄ and P₄ molecules – N=PP₄/PAs₄. Circles stand for experimental values taken from [8], stars stand for model values. JGa=7,79×10¹³ см^-2с^-1. Lines are drawn for easier perception of the figure.

The dependence of phosphorus fraction in solid GaP_xAs_1‑x(001) solution on substrate temperature is provided in [6]. The layers of the solid solution were generated with MBE using a flux of As₄ and P₂ from solid-state sources. The values obtained for As₄ from the analysis of [8] and for P₂ from matching of parameters on the basis of our experimental data. Fig 5. presents the dependence of x on TS.

Fig. 5. Dependence of phosphorus fraction in solid GaP_xAs_1-x solution depending upon substrate temperature. Circles stand for the experimental values taken from [6], stars stand for the model values.

The circles correspond to data of [6]; the stars stand for the values calculated on the basis of our model. Such a behavior of phosphorus fraction is well described by the model.

Thus, the analysis of the literature data shows that the existing conflicts and mismatches in results of different authors are explained by a wide variance in experimental conditions.

VI. Conclusion

The kinetic model describing the MBE-based formation of the composition of solid GaP_xAs_1- x solution in sublattice of V group is proposed on the basis of the analysis of the experimental data relating to impact of growth conditions on the composition of solid GaP_xAs_1- x solution. The model takes into account that growth of the crystal is accompanied with motion of the steps limiting terraces and growth islands. Rate of their motion is determined by the time, during which chemically adsorbed dimers of arsenic and phosphorus are accumulated at the surface of terraces and growth islands. The model adequately describes the behavior of phosphorus fraction in solid GaP_xAs_1-x solution, depending upon substrate temperature, value and relation of molecular fluxes. The experimental data found in the literature were analyzed on the basis of this model. It has been demonstrated that the existing conflicts result from a wide variance of experimental conditions used by different researchers. The model can be used for selection of growth conditions for layers of solid solution GaP_xAs_1-x(001) at a given phosphorus fraction.

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4. Tsao J.Y., Brennan T.M., Klem J.F. and Hammons B.E. Surface-stoichiometry dependence of As2 desorption and As4 “reflection” from GaAs(001) // J. Vac. Sci. Technol. A. – 1989. - V. 7. - N. 3. - P. 2138-2142.

5. Putyato М.А. Arsenic and Phosphorus Incorporation in Molecular Beam Epitaxy of Solid Solutions (AIII)PxAs1-x: Dissertation of candidate of physical and mathematical sciences. – Novosibirsk, 2006.

6. Tatsuoka Y., Kamimoto H., Kitano Y., Kitada T., Shimomura S., and Hiyamizu S. GaAs/GaAs0.8P0.2 quantum wells grown on (n11)A GaAs substrates by molecular beam epitaxy // J. Vac. Sci. Technol. B. – 1999. - V. 17. - N. 3. - P. 1155-1157.

7. Liang B.W., Tu C.W. A kinetic model for As and P incorporation behaviors in GaAsP grown by gas-source molecular beam epitaxy // J. Appl. Phys. – 1993. - V. 74. - N. 1. - P. 255-259.

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	Preobrazhenskii Valery Vladimirovich was born in Russia in I960. He received the M. S. degree in physics from Novosibirsk state University, in 1982, and the Ph. D. in solid-state physics from Institute of Semiconductor Physics, Novosibirsk, Russia in 2000. He has worked at Institute of Semiconductor Physics, Novosibirsk, Russia since 1985. He is currently a senior staff scientist of the laboratory of Molecular Beam Epitaxy of elementary semiconductors and AIIIBV-compounds and is involved in investigation of growth processes during MBE of A^IIIB^V-compounds.
	Boris R. Semyagin was born in Russia in 1961. He received the M. S. degree in physics from Novosibirsk state technical university in l988, and the Ph. D. in solid-state physics from Institute of Semiconductor Physics, Novosibirsk, Russia in 2003. He has worked at Institute of Semiconductor Physics since 1988. He is currently a member of the laboratory of the Molecular Beam Epitaxy of elementary semiconductors and A^IIIB^V-compounds and is involved in the MBE-growth of A^IIIB^V-compounds.
	Mikhail A. Putyato was born in Russia in 1962. He received the M. S. degree in physics from Novosibirsk state technical university, Novosibirsk, Russia in 1985 and he is currently having his post-graduate study at Tomsk state university, Tomsk, Russia. He has worked at Institute of Semiconductor Physics, Novosibirsk, Russia since 1989. He is currently a member of the laboratory of Molecular Beam Epitaxy of elementary semiconductors and A^IIIB^V-compounds and is involved in the processes of growth of A^IIIB^V MBE-heterostructures.
	Anton P. Vasilenko was born in Irkutsk, Russia, in 1977. He received the M.Sc. degree in physical electronics from Novosibirsk State Technical University, Novosibirsk, Russia, in 2000. Since 2003, he works in the Institute of Semiconductor Physics as a postdoctoral researcher. His main research interests are physics of semiconductors, X-Ray diffraction and x-ray topography.
	Dmitriy F. Feklin was born in 1978 in Novosibirsk, Russia. Have graduated from Novosibirsk State Technical University in 2001. He has worked at Institute of Semiconductor Physics, Novosibirsk, Russia since 1998. He is currently a member of the laboratory of the Molecular Beam Epitaxy of elementary semiconductors and A^IIIB^V-compounds and is involved in the MBE-growth of A^IIIB^V-compounds.
	Andrey V. Vasev is a Research Scientist in the Laboratory of molecular-beam epitaxy of elementary semiconductors and AIIIBV-compounds in the A.V. Rzhanov Institute of Semiconductor Physics SB RAS. He earned his Master’s degree of physics at Novosibirsk State University in 1998 and his Ph.D. in physics of semiconductors at the ISP SB RAS in 2010. His research interests include the RHEED and Ellipsometric investigation of processes occurring on semiconductors surface. His research has been supported by the Russian Foundation for Basic Research.
	Eugene A. Emelyanov was born in 1986 in Novosibirsk, Russia. Have graduated from Novosibirsk State Technical University in 2008. Now he is a postgraduate student of Institute of Semiconductor Physics, SB RAS. Since 2005 he has been working in research group of the laboratory of Molecular Beam Epitaxy of elementary semiconductors and A^IIIB^V-compounds from ISP SB RAS. E-mail(primary): [e-mail] E-mail (work): [e-mail]