INVESTIGATION OF THE HETEROEPITAXIAL INTERFACES IN THE GAINP/GAAS SUPERLATTICES BY HIGH-RESOLUTION X-RAY DIFFRACTIONS AND DYNAMIC SIMULATIONS

Two GaAs/GaInP superlattices grown on GaAs substrates by low-pressure metalorganic chemical vapor deposition have been studied using high resolution x-ray diffraction measurements and simulations by solving Tagaki-Taupin equations. The strained layers at both interfaces of the GaAs well are identified from the simulations of the measured diffraction patterns. The purging of indium at the interface of GaInP/GaAs accounts for the strained layer at the GaInP/GaAs interface while the pressure difference in the gas lines, which results in the different traveling time to the sample surface, is attributed to the indium-poor strained layer at the GaAs/GaInP interface. It is shown that high-resolution x-ray diffraction measurements combined with a dynamical simulation, are sensitive tools to study the heteroepitaxial interfaces on an atomic layer scale. In addition, the influence of a miscut of the substrate on the measurement is discussed in the article. It is shown that even though the miscut is small, the diffraction geometry is already an asymmetric one. More than 10% error in the superlattice period for a 2-degrees miscut substrate can result when the miscut substrate is considered a symmetric geometry.