Abstract: (Al,In)GaN quantum-disks and nanowires in the ultraviolet regime, and visible/near-infrared regime were implemented to address the hurdles in optical device technologies. The quantum-disks-in-nanowires form quantum-confined double-heterostructures with reduced piezoelectric polarization-fields (kV/cm) compared to planar InGaN quantum-wells (~MV/cm). The large specific area of InGaN axial nanowires further facilitates solar water splitting.