GaAsSbN layers with small lattice mismatch to GaAs were studied for possible application as the intrinsic layer in a GaAs-based p-i-n photodetector. Our calculation has shown that small lattice mismatch GaAsSbN to GaAs could be achieved at an Sb/N atomic ratio of 2.60. GaAsSbN was grown as the intrinsic layer for a GaAs/GaAsSbN/GaAs photodetector structure using solid-source molecular beam epitaxy in conjunction with a radio frequency (rf) plasma-assisted nitrogen source and valved antimony cracker source. The lattice mismatch of the GaAsSbN layer to GaAs was kept below 5000 ppm, which is sufficient to maintain coherent growth of ∼0.5 μm thick GaAsSbN on GaAs substrate. The growth temperature was varied between 420 and 520 °C, and the Sb flux beam equivalent pressure between 1.7×10-8 and 2.3×10-8 Torr to maintain coherent growth. All samples exhibit room temperature photocurrent response in the 1.3 μm wavelength region. X-ray diffraction two-dimensional maps showed diffuse scattering, which may have been caused by point defects in the material.