Material characteristics of self-assembled mushroom-like InGaN nanocolumns

The material characteristics of self-assembled mushroom-like N-polar InGaN/GaN nanowire heterostructure have been clarified, which were achieved by different In content self-assembled InGaN nanocolumns grown on self-assembled GaN nanocolumns template on (111)-silicon-substrate under N-rich condition by plasma-assist molecular beam epitaxy (PA-MBE). The In component of the InGaN nanocolumns was determined by XRD (2θ-ω scans). SEM has been used to study the morphology which demonstrated that the diameter of the nanocolumns became larger with higher In content. The structural properties of the individual InGaN nanocolumn were further analyzed by HAADF image, EDX and TEM. The high-In-content (85%) single mushroom-like InGaN nanocolumn showed some cracks on the sidewall, however the GaN nanocolumns showed dislocation free. The (0002) facet of the nanocolumn show very clearly hexagonal structure. It is quite clear that the formation of the mushroom-like InGaN nanocolumns comes from that the lateral epitaxy is dominating with the high In content embedded.