Owing to the remarkable structural, optical and magnetic properties, III-nitride-based materials, eventually doped with magnetic elements, have become technologically relevant building elements for state-of-the-art optoelectronics, high-power electronics and spintronics. While nitride-based optoelectronic devices for the visible and ultraviolet spectral range are widely established, all-nitride and In-free heterostructures active in the infrared (IR) are still a subject of investigation and likely to open wide perspectives for the next generation of devices. Lately, we have reported on the assembling of robust paramagnetic Mn-Mgk complexes in GaN co-doped with Mn and Mg, that beside offering the possibility to manipulate the spin-state of the system, reveal a room temperature emission in the IR spectral range relevant for telecommunication applications. In the perspective of realizing a reliable In-free nitride-based IR emitter, in this work we investigate the fundamental optical mechanisms lying at the origin of the observed IR emission from the Mn-Mgk complexes. The most efficient excitation channels for the IR emission are identified by combining experimental photoluminescence (PL) excitation spectroscopy and theoretical computational analysis based on density functional theory. Moreover, through reflectivity modeling, fabrication -in a metalorganic phase epitaxy process-, detailed structural -via atomic force microscopy, high resolution x-ray diffraction, transmission electron microscopy-, and optical -by means of spectroscopic ellipsometry, Raman and PL spectroscopies- characterization, AlxGa1-xN:Mn/GaN distributed Bragg reflectors (DBRs) are optimized and studied in combination with the GaN:(Mn,Mg) layers containing Mn-Mgk complexes. Further advancements towards a full-cavity heterostructure, in which an optically active layer is embedded between two nitride-based DBR structures during the same growth process, are performed. The analysis based on the full in-depth structural and optical characterizations allows to identify the challenges emerging during the fabrication process of the mentioned heterostructures and methods to overcome them, and to realize novel efficient IR devices.