Studies on InAs/GaSb superlattice structural properties by high resolution x-ray diffraction

Abstract

This paper presents work on InAs/GaSb superlattice structural property studies. The superlattice materials were grown by molecular beam epitaxy and measured by high resolution x-ray diffraction, and measured x-ray rocking curves were fitted to the simulated ones in order to fully analyze the superlattice structures. A four-layer model including an InAs layer, a GaSb layer and two interface layers was used for simulation. The results show that the two interface layers are ternary compounds of InSbAs, which have, respectively, an Sb composition of 0.99 at the InAs-on-GaSb interfaces and an Sb composition of 0.01 at the GaSb-on-InAs interfaces. This is the first article, to our knowledge, on the detailed analysis of the InAs/GaSb superlattice interface structures. The experiments also demonstrate that the As flux during the epitaxy growth affects the interface layer InSbAs compositions and hence the lattice mismatch between the superlattices and the substrates. With an As beam equivalent pressure change from 1 × 10−5 to 3 × 10−6 Torr, the lattice mismatch decreases from 3.2 × 10−3 to 5 × 10−4. Measurements on and analysis of Bragg peak broadening under different diffraction geometries show that the broadening depends on both the superlattice period and the lattice mismatch.