Carrier quantum confinement has been achieved in dilute nitrides by controlling the peculiar kinetics of hydrogen in those materials. GaAs 1− x N x/GaAs 1− x N x: H planar heterostructures have been fabricated by deposition of submicrometer titanium wires (width w= 485, 175, and 80 nm) on GaAs 1− x N x and subsequent H irradiation. Continuous-wave photoluminescence, PL, in ensembles of GaAs 1− x N x/GaAs 1− x N x: H heterostructures shows a blueshift of the PL peak energy and a marked increase in the PL radiative efficiency with decreasing one of the wire dimensions down to the nanometer-scale length. Concomitantly, time-resolved microphotoluminescence in single structures exhibits a pronounced slow down of carrier relaxation toward the ground state. All these results, supported by numerical calculations of H diffusion profiles, indicate that carrier quantum confinement can be achieved by H …