III-nitride nanowire heterostructure: an emerging solution for next generation all-color solid state light sources

InGaN/GaN nanowire (NW) heterostructures have emerged as a promising route to visible and ultraviolet optoelectronics beyond conventional planar III-nitride devices. Their three-dimensional geometry enables strain relaxation, reduces internal electric fields, and enables high-In-content active regions on a variety of substrates, while simultaneously introducing new challenges associated with surfaces and processing. This review summarizes recent progress on InGaN/GaN NW light-emitting diodes and lasers, covering bottom-up and top-down fabrication strategies, control of composition and morphology, and the processing of axial and radial device structures. We discuss their electrical and optical characteristics, including efficiency, carrier localization, surface recombination, and passivation, as well as emerging NW laser concepts based on novel cavity designs.