The optoelectronics applications of the Group III-nitrides have stimulated great interest in low-temperature epitaxial growth of GaN. As the quality of heteroepitaxial GaN films is limited by lattice mismatch between the film and typical substrates (e.g., sapphire and 6H-SiC), we have chosen to focus on homoepitaxial growth of epilayers on high-quality MOVPE-grown GaN substrates. Hyperthermal beams of neutral molecules (e.g., NH@sub 3@) are employed as alternatives to plasma and/or ion sources for low-temperature growth. Hyperthermal molecular beams with narrow energy distributions are generated by seeding heavy species in a supersonic expansion of a lighter gas (typically He or H@sub 2@). In this presentation, homoepitaxial growth of GaN using dual seeded supersonic molecular beams of NH@sub 3@ and triethylgallium (TEG) will be described. The results will be compared to those obtained using an NH@sub 3@-seeded supersonic molecular beam and a conventional Ga effusion cell. The influence of precursor kinetic energy on growth kinetics and film morphology will be discussed.