AlxGayIn1−x−yP withx+y=0.51, lattice matched to the GaAs substrate, has been grown by organometallic vapor phase epitaxy. The simple, horizontal, IR heated system operates at atmospheric pressure using the reactants TMAl, TMGa, TMIn, PH3, and H2. Alloys giving room temperature, band edge photoluminescence (PL) have been grown in the temperature range 625–780 °C. Emission wavelengths as short as 5820 A˚ (2.13 eV) are reported. High growth temperatures are found to give layers with the best surface morphology and PL intensity. The use of high temperatures is especially important for high Al content alloys. PL atx=0.2 is obtained only for temperatures above 740 °C.