Semiconductor nanowire arrays are used to replace the conventional planar layered construction for fabrication of LEDs and laser diodes. The nanowire arrays are formed from III-V or II-VI compound semiconductors on a conducting substrate. For fabrication of the device, an electrode layer is deposited on the substrate, a core material of one of a p-type and n-type compound semiconductor material is formed on top of the electrode as a planar base with a plurality of nanowires extending substantially vertically therefrom. A shell material of the other of the p-type and n-type compound semiconductor material is formed over an outer surface of the core material so that a p-n junction is formed across the planar base and over each of the plurality of nanowires. An electrode coating is formed an outer surface of the shell material for providing electrical contact to a current source. Heterostructures and superlattices grown along the lengths of the nanowires allow the confinement of photons in the quantum well to enhance the efficiency and as well as color tuning.