We have compiled the optical constants database for InxGa1-xAs which covers the composition range from 0.51 to 0.55 and the temperature range from 40 to 525 degrees-C. The InP substrate temperature was monitored by diffusive spectroscopy during the growth of the epitaxial layer. Ellipsometry was used to monitor the InxGa1-xAs composition over the entire temperature and composition range of the database. The composition monitored by ellipsometry is within 0.002 from the high resolution x-ray data with the exception of growth temperature at 440 degrees-C which is 0.005. We have also demonstrated the real time in situ feedback control of the InxGa1-xAs composition during epitaxial growth by using ellipsometry. The absolute accuracy of the InxGa1-xAs composition from the controlled experiment is 0.002. We can use this database to grow thick InxGa1-xAs layers grown on the InP substrates and can also use this as as in situ tool to fine tune the InxGa1-xAs composition before growth of the complicated structure.