In this paper, our studies about the optimization of the metalorganic vapor phase epitaxial growth process of GaInAs-InP hetero-interfaces are described. We have optimized the growth interruptions resulting in the growth of high quality quantum wells which show monolayer splitting in low temperature photoluminescence. By a careful evaluation of these spectra, we found strong evidence, that only the upper interface causes this monolayer splitting. This is further supported by results gained from quantum wells grown by selective area epitaxy. The lower interface obviously suffers from an unavoidable phosphorus/arsenic exchange which is even more pronounced in GaInP-GaAs structures. Shubnikov-de Haas experiments on optimized strained GaInAs-InP quantum well structures allowed the strain dependent evaluation of both, the electron and the hole masses.