Gate-all-around integrated circuit structures having germanium-doped nanowire/nanoribbon channel structures, and methods of fabricating gate-all-around integrated circuit structures having germanium-doped nanowire/nanoribbon channel structures, are described. For example, an integrated circuit structure includes a vertical arrangement of nanowires above a substrate. Individual ones of the vertical arrangement of nanowires have a relatively higher germanium concentration at a lateral mid-point of the nanowire than at lateral ends of the nanowire.