Homogeneous and heterogeneous thermal decomposition rates of trimethylgallium and arsine and their relevance to the growth of GaAs by MOCVD

The rate of decomposition of trimethylgallium (TMGa) and arsine is measured by sampled gas infrared absorption spectroscopy. The decomposition of TMGa is observed to go to completion at temperatures above 475°C as measured by the concentration of CH4 that is formed in the decomposition process. An activation energy of 58–62 kcal/mol is measured for the loss of the first methyl group. The decomposition of arsine is characterized by strong surface interactions. The activation energy for the decomposition of arsine in a quartz vessel is 34 kcal/mol. The activation energy for decomposition of AsH3 in the presence of GaAs wafers was found to be 18 kcal/mol. The implications of these results for the growth of GaAs by metalorganic chemical vapor deposition (MOCVD) are discussed.