This invention relates to a
nitride semiconductor epitaxial
wafer, its fabrication method, and optoelectronic devices. The
nitride semiconductor epitaxial
wafer comprises a substrate, a first n-type
nitride layer, a nitride
control layer, a composite
nanopillar structure layer, a nitride buffer layer, a second n-type nitride layer, a light-emitting layer, and a p-type nitride layer, stacked sequentially. The composite
nanopillar structure layer includes a first
nanopillar spacer unit and a second nanopillar spacer unit. The height of the first nanopillar spacer unit is greater than the height of the second nanopillar spacer unit. The first nanopillar spacer unit includes a first
metal microstructure, a first nanopillar, and a first top unit. The second nanopillar spacer unit includes a second
metal microstructure, a second nanopillar, and a second top unit. By adopting the solution provided by this invention, the probability of
dislocation extension to the light-emitting layer is reduced, leakage channels are reduced, and radiative recombination is enhanced, thereby improving the brightness, leakage current, and ESD antistatic
discharge performance of the epitaxial
wafer.