By using lattice matched short period (50 Å) GaInAs/InP superlattices, we are able to extensively characterize, ex-situ, nucleation of thin (20–30 Å) GaInAs layers on InP. Systematic variation of the interface formation technique allows us to understand how parameters such as growth temperature and growth rate can contribute to interfacial roughness, giving rise to growth transients near the interfaces that are unexpected from characterization of thick layers. Growth of multi-period structures such as those studied here enables the use of Raman scattering, photoluminescence, and double crystal x-ray diffraction to determine that Ga incorporation is favored over In incorporation near the InP to GaInAs interfaces. Furthermore, by examining the surfaces and structural properties of epitaxial layers (15 Å-1 μm) of both InP and GaInAs with atomic force microscopy and Raman scattering, respectively, we are able to correlate results on the superlattice structures with results from single layers. Finally, we show how understanding the nucleation of thin films through the process described here enables the growth of complicated, previously unrealizable, heterostructures for use in novel optoelectronic devices.