FOURIER-TRANSFORM INFRARED SPECTROSCOPIC STUDY OF PREDEPOSITION REACTIONS IN METALLOORGANIC CHEMICAL VAPOR-DEPOSITION OF GALLIUM NITRIDE

The predeposition reactions that occur during metalloorganic chemical vapor deposition (MOCVD) of gallium nitride (GaN) were studied with Fourier transform infrared (FTIR) spectroscopy. The reactants studied included trimethylgallium (TMGa), ammonia (NH3), and nitrogen trifluoride (NF3). At room temperature, the predeposition reaction between TMGa and NH3 went to completion immediately after mixing. The resulting adduct, TMGa:NH3, was easily observed in the gas phase via FTIR spectroscopy. Assignments have been made to the IR absorption bands of gaseous TMGa:NH3. At 150-degrees-C, chemical equilibrium was reached between the gaseous adduct, TMGa:NH3, and the reactants. The forward rate constant of this predeposition reaction is 5.89 x 10(-3) Torr s)-1. No evidence of gas-phase adduct formation was observed when NF3 was mixed with TMGa at room temperature and 150-degrees-C. This suggests a potential advantage of NF3 over NH3 as a nitrogen source in MOCVD of GaN.