RP-CVD epitaxy plays an important role in microelectronics because it allows the growth of heavily doped layers while maintaining the crystalline orientation of the starting substrate. A good control of these layers is mandatory to ensure the reliability of the devices. In particular, heavily doped epitaxial layers of Si or SiGe are needed to reduce contacts resistivity. The objective of this thesis is to develop a characterization technique able to measure the dopants concentration and their chemical environment which determines whether they are electrically active or not. The work will consist in evaluating X-ray photoelectron spectroscopy (XPS) to quantify dopants such as As, P and B and identity they chemical state. The impact of growth parameters, particularly the temperature and the precursors, will be evaluated to obtain heavily doped thin films without morphological degradation while minimizing inactive dopants concentration. Methodological developments will be carried out with XPS to obtain a reproducible and in-line characterization of the doping. Experimental conditions and spectra post-treatments will be optimized. The PhD student will also do exploratory measurements using hard X-ray photoelectron spectroscopy (HAXPES). Other characterization techniques such as SIMS, FTIR and XRD as well as electrical measurements will complement the results.