In the past few years, tremendous progress has been achieved on epitaxial growth and processing of group III nitride nano- and microrods. Furthermore, these growth improvements have allowed the fabrication of optoelectronic devices based nanorods as active elements, i.e. light emitting diodes (LEDs). However, their efficiency is still far behind the performance of conventional GaN-based light emitting diodes.
The controlled growth of GaN nanorods offers a potential benefit for achieving higher efficiencies of III-Nitride based optoelectronic devices due to a high surface to volume ratio. Nanorods have a very large active area compared to their footprint. Since the active region is wrapped around the three-dimensional core (for core shell structures), the active layer scales with the rod’s aspect ratio (i.e. the ratio of height and diameter). Therefore, by controlling their density, diameter and height, a tremendous increase of active surface can be achieved. Additionally, the low defect density in nanorods allows the characterization of single extended defects which is of high interest for a clear understanding of the formation of these defects.
In this study we present a direct nano-scale correlation of the optical properties with the actual real crystalline structure of single GaN nanorods using low temperature CL spectroscopy in a scanning transmission electron microscope (STEM). We concentrate on the crystalline quality, local In incorporation, n- and p-layer quality and defects of the complete structures.