Gas Phase Studies of Trimethylgallium with Ammonia, Propylamine and Water at Elevated Temperatures: Towards an Understanding of GaN Growth and Oxygen Incorporation

Abstract

The reactions between trimethylgallium (TMG) and three reactants were studied to provide some insight into the reaction mechanism of gallium nitride growth and oxygen incorporation. All reactions were studied in a flow reactor. The gas phase was analyzed by molecular beam sampling mass spectrometry. Ammonia is a widely used precursor for the deposition of GaN films. In the gas phase, different gallium- and nitrogen-containing species were detected as a function of temperature. Propylamine is pyrolyzed at lower temperatures than ammonia and could therefore provide a low-temperature route towards GaN. In the reaction of TMG with propylamine, a different behavior was found; only simple adducts with one gallium atom per molecule were detected, which were instable at higher temperatures. The reaction of TMG with water is an important side reaction, because water is the main impurity of ammonia and could thus be the main reason for the high oxygen levels found in GaN films.