Bulk lattice parameter and band gap of cubic InXGa1−XN (001) alloys on MgO (100) substrates

•Cubic InxGa1−xN.•Bulk lattice parameter.•Optical band gap.•Molecular beam epitaxy.

InxGa1−xN (001) ternary alloys were grown on GaN/MgO (100) substrates in a plasma assisted molecular beam epitaxy system. We determined the in-plane [001] and in-growth [110] lattice parameters, as well as the bulk lattice parameter of the alloys for different In concentrations by high resolution X-ray diffraction. The In concentration was determined assuming Vegard׳s law for the alloy lattice parameter. The optical energy gap of InxGa1−xN has been determined by transmittance measurements from absorption edges for several In concentrations. Our results show that the alloys have a direct band gap for all In concentrations and a bowing parameter b=1.84.