The ternary InxGa1-xSb epilayers grown on GaAs substrates by metalorganic chemical vapor deposition using a GaSb buffer layer have been demonstrated. High-resolution transmission electron microscopy micrographs illustrate an entirely relaxed GaSb buffer grown by the interfacial misfit dislocation growth mode. A high quality In0.15Ga0.85Sb epilayer was obtained on the GaSb surface with the very low threading dislocation densities (∼8.0 × 106cm-2) and the surface roughness was 0.87 nm. The indium content of the InxGa1-xSb epilayer depends significantly on the growth temperature and approaches to a saturated value of 15% when the growth temperature was above 580 °C. Based on the X-ray photoelectron spectroscopy analyses, the valence band offset and the conduction band offset of Al2O3 with the In0.15Ga0.85Sb/GaSb/GaAs heterostructure are 3.26 eV and 2.91 eV, respectively. In addition, from the O1s energy-loss spectrum analysis, the band gap of Al2O3 is found to be ∼6.78 ± 0.05 eV.