Exploring the optimum growth conditions for InAs/GaSb and GaAs/GaSb superlattices on InAs substrates by metalorganic chemical vapor deposition

The effect of growth parameters in metalorganic chemical vapor deposition (MOCVD) on the crystal quality and surface morphology of the InAs/GaSb superlattices (SLs) on InAs substrates was systematically investigated by X-ray diffraction, scanning transmission electron microscopy, atomic force microscopy and photoluminescence. It was found that InAs/GaSb SLs grown at 530 °C with intentionally-formed GaAs-type interfaces exhibited lattice mismatch as low as −0.01%, abrupt SL interfaces and atomically smooth surface with a root mean square roughness of only 0.136 nm. Clear photoluminescence was observed around 8 μm at 77 K for a long-wavelength SL structure. The nominal thickness of the GaAs-type interfacial layers and the overall SL strain can be effectively controlled by tuning the AsH3 flow rate. In addition, high-quality GaAs/GaSb SLs on InAs substrate were demonstrated as a replacement of the GaAsSb alloys. An AsH3-purge step was introduced after GaSb growth to form GaAs layers via As-Sb exchange. An optimal condition has resulted in lattice-mismatch of 0.21% and surface roughness of 0.122 nm for the GaAs/GaSb SLs.