Growth and characterization of ultrathin GaP layer in a GaAs matrix by X-ray interference effect

Abstract

An ultrathin two monolayers thick layer of GaP sandwiched within a GaAs matrix was grown by atomic layer molecular beam epitaxy (ALMBE). The X-ray interference effect (Pendellösung) was used to determine the structural parameters such as thickness, lattice parameter, chemical composition, and strain. Excellent agreement between the experimental rocking curve and the simulation using the dynamical theory of X-ray diffraction was found indicating the high quality of the sample. Analysis of the scans in symmetrical (004) and asymmetrical (224) reflections, sensitive to both perpendicular and parallel strain, shows that the GaP layer is coherent with the substrate, i.e., it is below the critical thickness in agreement with critical thickness theories. Despite the competition for incorporation between arsenic and phosphorus the experimental GaP thickness is found to be identical to the nominal growth value, demonstrating full incorporation of phosphorus when growing by ALMBE. No significant out-diffusion or segregation of P is observed.