High-Resolution X-ray Diffraction Studies of ZnSnAs2 Epitaxial Films Nearly Lattice-matched to InP Substrates

ZnSnAs2 epitaxial films were grown by molecular beam epitaxy (MBE) on nearly lattice matched InP substrates. Four samples namely samples A, B, C, and D were prepared at different growth times of 15, 30, 50, and 83 mins, respectively, using the optimum growth conditions earlier reported to obtain samples of different values of thickness for the purpose of structural characterization using High-Resolution X-ray Diffraction (HR-XRD). HR-XRD investigations revealed unrelaxed lattice constant a⊥ values along the growth direction of 5.8991 Å, 5.8991 Å, 5.8886 Å, and 5.8928 Åfor samples A, B, C, and D, respectively. Reciprocal Space Mapping on one of the samples indicates pseudomorphic growth with respect to the InP substrate. The absence of full-width at half maximum (FWHM) broadening of the of the HR-XRD rocking curves with increasing thickness of the samples suggests that all the epitaxial films in this work are pseudomorphic with the InP substrate. Assuming a Poisson ratio ν of 1/3, the corrected values of the lattice constant, i.e. values of the free-standing lattice constant afs, were calculated to be 5.8840 Å, 5.8840 Å, 5.8788 Å, and 5.8809 Åfor samples A, B, C, and D. These results suggest that the elongation due to the pseudomorphic growth is substantial in the computation of the true lattice constant of ZnSnAs2 epitaxial films.