High Aspect Ratio GaN Fin Microstructures with Nonpolar Sidewalls by Continuous Mode Metalorganic Vapor Phase Epitaxy

Three-dimensional GaN micro- and nanorods with high aspect ratio have recently gained substantial interest in LED research, due to their reduced defect density, their non-polar sidewalls and their increased active area. Here, we present an alternative geometry for high aspect ratio 3D nanostructures: vertically standing GaN “walls”, so called GaN fins. With high aspect ratios, these GaN fins exhibit the same interesting characteristics as their rod counterparts mentioned above. Beyond that, due to their geometry, the respective material analysis and device processing can be expected to be less complex. We are able to demonstrate the highly reproducible selective area growth of these fins by continuous mode MOVPE. Fin heights of more than 50 µm (aspect ratios of nearly 14) could be achieved and growth rates are as high as 22.8 µm/h in the beginning of the growth. The sidewalls are smooth non-polar <11-20> a-planes, suitable for optoelectronic devices due to the missing quantum-confined Stark effect and less edge effects compared to rods. We investigate the influence of pattern orientation and geometry on the fin morphology. Moreover, the influence of silane flow, which is known to enhance the vertical growth rate, and other growth parameters are systematically explored.