We report on the successful growth of GalnP on GaAs substrate by Atomic Layer Epitaxy using organometallic and hydride sources. Growth was achieved by sequential exposure of the substrate to TMGa, PH3, TEIn and PH3. X-ray diffraction showed compositional lattice-matching optimally at 550°C with arbitrary choices of the mole fractions of the precursors in the gas phase. TEM also confirmed the highest ordering at this growth temperature on (100) substrates. Uniformity was excellent using Atomic Layer Epitaxy. Growth on (111)A GaAs substrates produced no evidence of the ordered CuPt phase present on (100) substrates.