Photochemical Vapor Deposition of Wide Bandgap III-V Materials: Influence of Photochemically Generated Radicals on the Growth of Aluminum Nitride and Gallium Nitride Films

Aluminum nitride and gallium nitride films have been grown on the 1120, 0001, 1010, and 1102 (A, C, M, and R, respectively) planes of sapphire by laser photochemical vapor deposition and MOCVD at temperatures ranging from 600 to 950°C and a total reactor pressure of 1-5 Torr. For the molecular precursors triethylgallium (TEGa) and ammonia, GaN film growth directly onto sapphire or on AlN buffer layers ranging from ∼50 to 500 Å in thickness has been investigated under conventional MOCVD growth conditions and compared to the growth rates and structure for films produced when 193 and 248 nm (ArF, ℏω = 6.4 eV, and KrF, ℏω = 5.0 eV, respectively) photons are introduced into the reactor. Kinetic modeling of the growth rate dependence on laser pulse energy suggests that the dominant photolytically produced species is the amidogen radical, NH₂. The presence of 193 nm photons also promotes the growth of (1120)-oriented GaN films, which provides an example of the ability of photochemistry in the gas phase to drive surface kinetics.