Growth of GaN single crystal substrates

Self-separating single crystal GaN substrates were grown by hydride-metalorganic vapor phase epitaxy (H-MOVPE) on closely lattice-matched LiGaO2 substrates. A critical process for obtaining high quality GaN films on LiGaO2 was the initial surface nitridation of the oxide substrate with NH3. This nitriding process and the cooling schedule after growth were critical to achieving film-substrate self-separation. The as-grown single crystal GaN substrate exhibited a flat surface without any mechanical or chemical treatment. No cracks or residual strain were observed. Different characterization techniques were used to assess the quality of the substrates and films quality. The surface morphology was examined by AFM and the structural quality was analyzed by XRD; the chemical composition was investigated by AES, ESCA, SNMS and SIMS were used to determine composition profiles near the surface. Micro Raman spectroscopy was applied for film and substrate characterization.