Investigation of composition uniformity on thickness of GaInAsP layers grown on InP substrates by vapor-phase epitaxy

GaInPAs/InP heterostructures grown by low pressure (0.1 bar, 600$^\circ$C) metal-organic chemical vapor phase deposition were investigated. The thicknesses of grown GaInAsP layers were about 1 $\mu$m. For the epitaxial layers Ga$_{1-x}$In$_{x}$P$_{1-y}$As$_{y)}$ with average compositions of $x$ = 0.77 – 0.87 and $y$ = 0.07 – 0.42 the variation of V group elements content y with the epilayer depth were revealed, weher the compositions of V-group elements were changed up to $\Delta y$ = 0.1 atomic fractions in V group elements sublattice. In most cases, y change occurs in a GaInAsP region up to 200 nm thick adjacent to the InP. In some cases, y changes throughout the whole GaInPAs layer thickness. Fo the epitaxial layers with a satisfactory crystal perfection the less was the mismatch between the substrate and the GaInPAs epitaxial layer, the smaller was the value of $\Delta y$. For GaInPAs layers characterized by a low degree of crystal perfection and a high lattice mismatch between GaInAsP and InP layers, the value of $\Delta y$ was about zero. These data let us suggest that the incorporation of atoms of the V group in the epitaxial layer strongly depends on elastic deformation of the growing monolayer, that is mismatched with the underlying crystal surface.