DIFFUSIVITY AND THERMAL-CRACKING RATE OF METALORGANIC GASES BY CHROMATOGRAPHY

Metalorganic gases such as trimethylaluminum (TMA), trimethylgallium (TMG), triethylaluminum (TEA), and triethylgallium (TEG) are often used as metal sources of chemical vapor deposition for producing epitaxial thin films of GaAs or GaAlAs. Film growth kinetics are governed by thermal cracking of those gases in a thermal boundary layer which is expected to develop on the heated substrate and also by diffusion of those gases from the bulk stream into the boundary layer. The method of moment was used to analyze chromatographic elution curves and measurements at different temperature ranges provided diffusivities (293-428 K) and thermal cracking rate coefficients (454-580 K) of the four gases in hydrogen stream.