The capability to grow bulk lattice matched material, with band gap energies less than that of GaAs, is of interest for applications in concentrated photovoltaic devices. Material development is this area has focused on the incorporation of dilute amounts of nitrogen into conventional III/V crystals, although short minority carrier diffusion lengths, narrow depletion widths, deep level defects and high carbon incorporation have limited the performance in MOVPE grown devices. The ability to grow narrow band gap material free of nitrogen would be advantageous for the electronic properties of these devices. Quinternary materials, although complex, offer a higher degree of freedom for materials development with knowledge of the incorporation properties of constituent elements. Recent reports of this material system were in the growth of mid-infrared light emitting diodes on GaSb substrates by liquid phase epitaxy (LPE) [1,2]. To our knowledge, there have been no reports of this material grown lattice matched GaAs by MOVPE. Growth studies have been performed on GaInAsSbP thin film alloys, grown on (100) GaAs substrates by MOVPE utilizing liquid group III and group V metal organic precursors. Room temperature photoluminescence studies of nominally lattice matched material to (100) GaAs substrates exhibits a band gap energy of 1.37 eV(Ga<SUB>(0.76)</SUB>In<SUB>(0.24)</SUB>As<SUB>(0.25)</SUB>Sb<SUB>(0.025)</SUB>P<SUB>(0.725)</SUB>, Δa/a=8.4×10<SUP>-4</SUP>, V/III=67). High resolution x-ray diffraction (HRXRD), ω-2θ rocking curves around the (004) reflection for GaAs, were used to determine the lattice mismatch of the out-of-plane lattice parameter of the GaInAsSbP films. Due to the complex nature of the GaInAsSbP alloy, it is difficult to determine the composition by conventional measurements and assuming Vegard’s Law. Therefore, calibrated secondary ion mass spectroscopy (SIMS) was used on selected samples to determine the actual solid phase compositions of the GaInAsSbP material. Future work with this material system will be to determine the lowest possible band gap energy for lattice matched material and to evaluate the effects of dilute amounts (<1%) of nitrogen into the GaInAsSbP material. This work is funded by Army Research Lab (ARL), contract number W911NF-09-2-0008. 1. A. Krier, V. M. Smirnov, P. J. Batty, M. Yin, K. T. Lai, S. Rybchenko, S. K. Haywood, V. I. Vasil’ev, G. S. Gagis and V. I. Kuchinskii, Appl. Phys. Lett. 91, 082102 (2007). 2. A. Krier, V. M. Smirnov, P. J. Batty, V. I. Vasil’ev, G. S. Gagis and V. I. Kuchinskii, Appl. Phys. Lett 90, 211115 (2007).