The molecular beam epitaxial (MBE) growth and spectroscopy of dilute nitride InAsN:Sb epilayers are presented. Nitrogen incorporation in InAsN epilayers grown by radio-frequency plasma-assisted MBE was investigated as a function of growth conditions. High-quality InAsN epilayers containing up to 2.5% nitrogen were successfully grown using optimal growth conditions. The optical properties of InAsN were studied by photoluminescence (PL). Intense PL emission at 4% K was observed with double-peak features, which were attributed to free carrier recombination and localised carrier recombination. Strong room temperature PL emission extending up to a wavelength of 4.5% �¿m was obtained and a bandgap reduction of 63% meV for 1% N was deduced. The electronic properties of InAsN such as residual carrier concentration and mobility were also studied by Hall effect measurements. Further improvement of InAsN by addition of Sb during growth is also discussed. The authors observed that the introduction of Sb flux dramatically enhances nitrogen incorporation and significantly improves optical properties. In addition, Sb incorporation is enhanced with the presence of nitrogen. The authors also report the realisation of InAsN:Sb/InAs mid-infrared light emitting diodes operating at 4.0% �¿m at 4% K.