Abstract
Reactive chemical gas-phase intermediate species important in the metalorganic chemical vapor deposition growth process of GaAs have been identified for the first time using in situ ultraviolet absorption spectroscopy. Spectral features from Ga, GaH, and GaCH3 were observed during thermal decomposition of trimethylgallium (TMGa) in hydrogen gas. Evidence for free radical reactions involving CH3 and H in the pyrolysis of TMGa is presented. The addition of arsine to the mixture is found to change the reaction pathways as evident from the production of AsH2 and the disappearance of Ga and GaH. Gas-phase decomposition of the metalorganic species in hydrogen can produce gallium under the conditions of high pressure atomic layer epitaxy.