Various embodiments of the present disclosure pertain to selective photo-enhanced wet oxidation for nitride layer regrowth on substrates. In one aspect, a method may comprise: forming a first III-nitride layer with a first low bandgap energy on a first surface of a substrate; forming a second III-nitride layer with a first high bandgap energy on the first III-nitride layer; transforming portions of the first III-nitride layer into a plurality of III-oxide stripes by photo-enhanced wet oxidation; forming a plurality of III-nitride nanowires with a second low bandgap energy on the second III-nitride layer between the III-oxide stripes; and selectively transforming at least some of the III-nitride nanowires into III-oxide nanowires by selective photo-enhanced oxidation.