This work is a contribution to the investigation of the spin properties of III-V semiconductors with possible applications to the emerging semiconductor spintronics field. Two approaches have been explored in this work to achieve a long and robust spin polarization: i) Spatial confinement of the carriers in 0D nanostructured systems (quantum dots). ii) Defect engineering of paramagnetic centres in a bulk systems. Concerning the first approach, we investigated the polarization properties of excitons in nanowire-embedded GaN/AlN quantum dots. We evidence a sizeable and temperature insensitive...