The present disclosure relates to semiconductor structures and, more particularly, to uniform semiconductor nanowire and nanosheet light emitting diodes and methods of manufacture. The structure includes a buffer layer; at least one dielectric layer on the buffer layer, the at least one dielectric layer having a plurality of openings exposing the buffer layer; and a plurality of uniformly sized and shaped nanowires or nanosheets formed in the openings and extending above the at least one dielectric layer.