THERMAL-DECOMPOSITION STUDIES OF GROUP-V HYDRIDES

The decomposition of phosphine and arsine was studied by spontaneous Raman spectroscopy in a standard atmospheric pressure MOVPE reactor. Raman spectroscopy made it possible to characterize the gas phase, from a thermal and a chemical point of view, above and below the hot susceptor. Decomposition curves of AsH3 and PH3 are given. Based on the results obtained for PH3 and on the great similarity between PH3 and AsH3 structures and observable behaviour, an interpretation of the decomposition process of PH3 and AsH3 is given. Moreover, the presence of hydrogenated intermediate species such as AsH2 and PH2 is shown to be probably at the origin of a partially reversible reaction with AsH3 and PH3. This equilibrium was pointed out by the re-formation of AsH3 and PH3 under the susceptor where the temperature decreases.