Effect of Al pre-deposition on AlN buffer layer and GaN film grown on Si (111) substrate by MOCVD

In this study, we investigated the effect of Al pre-deposition time on GaN crystal quality. The GaN layer was grown on a Si (111) substrate by metal organic chemical vapor deposition using an AlN buffer layer. Atomic force microscopy, scanning electron microscopy and x-ray diffraction were used to evaluate film growth. Consequently, we found significant differences in the epitaxial properties of the AlN buffer and GaN layer, which were dependent on the Al pre-deposition time. When the deposition time was 0 s, the AlN buffer layer was very smooth, but the GaN layer did not have a high crystal quality. At a Al pre-deposition time of 60 s, the AlN buffer started to be transformed into a rough surface and the GaN layer had both a mirror-like surface and better crystal quality. When the Al pre-deposition time was greater than 120 s, GaN surfaces had a high roughness. In addition, the surface morphology of the GaN had not coalesced. Based on these results, the optimized Al pre-deposition time was found to be essential to achieve an appropriate surface roughness for high crystal quality of GaN.