Low temperature growth of gallium nitride on quartz and sapphire substrates

Gallium nitride films have been grown using combined ultraviolet excimer laser and microwave plasma enhanced metalorganic chemical vapour deposition. A range of growth conditions was used, including low substrate temperatures between 380 degrees C and 625 degrees C, which enabled the use of quartz substrates, in addition to more common r-plane sapphire. Films grown on quartz and on sapphire were characterised using X-ray diffraction, Raman spectroscopy and optical transmission. Evidence is given that layers grown on quartz have similar structural and optical quality as those grown on sapphire, and both contain large-scale, oriented crystallites embedded in the microcrystalline, randomly oriented medium with intermediate range order and cubic symmetry. The disorder correlates well with the substrate temperature during growth.