RESUMO
The spatial distribution of photon modes confined in a 0D cavity and a 1D W1 waveguide is investigated on AlN-based photonic crystal (PC) membranes by spectrally resolved scanning confocal microscopy in the ultra-violet spectral range. The influence of the fabrication-induced disorder of the PC on the photon modes is analyzed. The cavity modes are shown to be robust with respect to disorder, whereas the 1D modes of the W1 waveguide are localized near its cut-off frequency. Those modifications of the lowest energy photonic modes are compared to simulations of weakly disordered photonic structures.
RESUMO
The structural and optical properties of InGaN/GaN nanowire heterostructures grown by plasma-assisted molecular beam epitaxy have been studied using a combination of transmission electron microscopy, electron tomography and photoluminescence spectroscopy. It is found that, depending on In content, the strain relaxation of InGaN may be elastic or plastic. Elastic relaxation results in a pronounced radial In content gradient. Plastic relaxation is associated with the formation of misfit dislocations at the InGaN/GaN interface or with cracks in the InGaN nanowire section. In all cases, a GaN shell was formed around the InGaN core, which is assigned to differences in In and Ga diffusion mean free paths.
