High-resolution X-ray diffraction studies of the GaAs structures grown at a low temperature and periodically δ-doped with antimony and phosphorus

High-resolution X-ray diffractometry is used to study the GaAs structures grown at a low temperature (LT-GaAs) by molecular beam epitaxy. The feature of the studied structures is the presence of thin (about 1 monolayer) layers delta-doped with isovalent Sb and P impurities and formed at a low epitaxial temperature. The delta-doped layers periodically arranged in the bulk of the epitaxial film form the X-ray diffraction pattern containing a large number of interference peaks, whose quantitative analysis allows one to extract the information on the thickness, chemical composition, and abruptness of layer boundaries. Such an analysis was performed before and after annealing of the studied samples, and this annealing gives rise to a system of As nanoinclusions (quantum dots) in the bulk of the epitaxial film. The variations in the parameters of diffraction curves that characterize the process of formation of the As quantum dots are revealed. It is established that the formation of the system of As quantum dots in LT-GaAs (delta-Sb) causes enhanced damping of super-lattice satellite peaks, which is probably associated with an increase in the roughness and diffusion spreading of the layers delta-doped with Sb. A similar phenomenon was not observed in LT-GaAs (delta-P), which is most probably caused by the absence of heterogeneous precipitation of As in the layers delta-doped with P and lower effective coefficients of diffusion intermixing As-P compared with As-Sb. For the samples with a combined system of the layers delta-doped with Sb and P, the diffraction curves quantitatively confirmed the formation of superlattices containing the system of As quantum dots, in which the mismatch with respect to the GaAs substrate by the average lattice parameter is less than 0.0001%.