InGaAsP/InP and InGaAsP/InAsP multilayers were grown on InP(001) by low-pressure organometallic vapor phase epitaxy. Large growth rates of approximate to 0.4-0.6 nm s(-1) and an increased element-V overpressure were used to limit the morphological evolution of the strained layers during growth and to compensate for the relatively high temperatures (approximate to 630 degrees C) necessary for vapor phase epitaxy in a diffusion-limited regime. High-resolution x-ray diffraction and reciprocal lattice mapping analyses indicate fully strained multilayers of high crystalline quality. This structural information, combined with room-temperature photoluminescence (PL) measurements, allows us to determine accurately the thickness and the composition of the layers. Well-resolved excitonic transitions between the heavy- and light-hole valence bands and the conduction band are visible in the low-temperature optical absorption spectra for compressive InGaAsP/InP multilayers. The PL spectra for compressive InGaAsP/InP structures show sharp and intense transitions between the first confined levels in the conduction and the heavy-hole bands. The PL peaks for InGaAsP/InAsP heterostructures are slightly broader than for InGaAsP/InP multilayers due to the more complex (quaternary-ternary) interface but remain sharp and intense.