Effects of in-situ UV irradiation on the uniformity and optical properties of GaAsBi epi-layers grown by MBE

•In-situ UV irradiation of GaAsBi reduces clustering of incorporated bismuth atoms.•UV irradiation also produces abrupt interfaces and uniform epi-layer compositions.•Increased cluster related luminescence with decreasing incident UV fluence.•Reduced cluster states results in improved optical properties of GaAsBi alloys.•Incident UV irradiation discussed in terms on its effect on surface reconstruction.