Characterization of GaN layers grown on metallic TiN buffer layers

The epitaxial, continuous, flat GaN layers were recently found to be grown on the metallic TiN buffer layers. In the present experiment, the GaN layers grown on TiN were characterized using the X-ray diffraction method and transmission electron microscope and the results were compared with those grown on the AlN buffer layer. The TiN and GaN layers exhibited [111] and [0001] fiber textures, respectively. The GaN layers provided large half-value widths of the X-ray diffraction peaks of both the (0002) and {101̄0} planes compared with those of the GaN layers grown on AlN. This may be explained by a large lattice mismatch between GaN and TiN of about 6.2% compared with that between GaN and AlN. The GaN layers grown on TiN provided a low density of domains with opposite lattice polarity and horizontal dislocations (10⁸ -10⁹ cm^-2). Although a density of the horizontal dislocations was similar to that of the threading dislocations in the GaN layers grown on AlN, the GaN layers grown on TiN produced a significant reduction of threading dislocation density compared with the GaN layers grown on AlN. This suggests that the direct growth of GaN on TiN would become the technique to reduce the threading dislocation density in the GaN layers.