The results of laser-assisted reactivity in constrained gas expansions involving either triethylgallium (TEGa) or trimethylgallium (TMGa) with ammonia are reported. NH3 (or ND3) along with TEGa or TMGa are introduced into a high vacuum chamber through a customized dual-source pulsed nozzle assembly. Excimer laser output (193 or 248 nm) is focused into the mixing and reaction region of the nozzle source, and a quadrupole mass spectrometer interrogates the photolyzed expansion. During gas mixing and expansion into the vacuum, the adduct signals from TMGa:NH3 or TEGa:NH3 are observed when the nozzle assembly is cooled. Laser irradiation of the gas mixtures results in the formation of new adducts, TMGa:NH2 or TEGa:NH2, and diverse, higher mass GaN-containing species. Power and wavelength dependence studies are used to reveal the photolytic origins of individual mass spectral features, and the influence of sample pressure on cluster formation processes is also examined.