Trimeric diethylgallium amide (Et2GaNH2)3 has been used for the growth of highly crystalline GaN films by cold wall low-pressure MOCVD in the low-temperature range of 500−700 °C and at pressures 77−177 mbar on Si(100) and polycrystalline Al2O3 substrates. The thickness of GaN films ranged from 6 to 8 μm, the growth rates varied from 7 to 8 μm/h. Films deposited at lower temperatures (500−550 °C) had a pale yellowish color and were amorphous. At 600 °C slightly gray colored films were obtained, while above 650 °C high-quality crystalline films were formed, having characteristic hexagonal wurtzite structure diffraction patterns. The films are consistent with the 1:1 stoichiometry of GaN and have carbon and oxygen as impurities; however, cracks were not evident on the surface by SEM examination up to a magnification of 30 000. In contrast, samples of GaN deposited under high-vacuum conditions (up to 10-2 mbar) have neither a 1:1 stoichiometry nor a smooth surface morphology. Atomic force microscopy, scanning electron microscopy, Auger electron microscopy, and energy-dispersive X-ray analyses were used for the study of the structure, composition, and morphology of the films. [449]