Self oriented growth of GaN films on molten gallium

In this paper, a concept of self-oriented growth of GaN film on molten Ga films is reported. The nitridation of molten Ga films on amorphous quartz substrates using atomic nitrogen at low pressures produced c-plane self-oriented films. The sizes of individual GaN hexagonal platelet shaped crystals within a 19 μm thick film were about 4-5 μm. Micro-Raman spectra showed a peak at 144.6 cm^-1 indicating the wurtzite phase of the resulting GaN. XRD θ-2θ scans showed only reflections of (0002) and (0004) planes indicating c-plane orientation over an area exceeding 25 mm². The cross-sectional SEM images clearly showed the presence of molten gallium layer between the self-oriented GaN layer and the quartz substrate. Cross-sectional TEM analysis suggested that the resulting GaN film was single crystalline and also did not contain dislocation crops. However, the Kikuchi line analysis using convergent beam electron diffraction showed mis-orientation of about 10 degrees between the neighboring grains and about 2 degrees or less between the alternating grains.