In dilute nitrides [e.g., Ga(AsN), (InGa)(AsN)] the formation of stable N-2H-H complexes following H irradiation removes the effects nitrogen has on the optical (i.e., refractive index [1]), structural [2], and electronic [3] properties of the material. In particular, H binding to N atoms in GaAs1−xNx leads to an increase in the band gap energy of the N-containing material (∼1.33 eV for x = 1% at T = 5 K) up to the value it has in GaAs (1.52 eV at 5 K). Therefore, by allowing H incorporation only in selected regions of the sample – e.g., by deposition of H-opaque masks prior to the hydrogenation – it is possible to attain a spatially controlled modulation of the band gap energy in the growth plane.
This technique, referred to as in-plane Band Gap Engineering, can be employed to tailor the carrier-confining potential down to a nm scale, resulting in the fabrication of site-controlled, dilute nitride-based quantum dots (QDs). We demonstrate here that such QDs emit single photons on demand, as revealed by measuring the second-order correlation function of the single-exciton emission [4].Coupled to the possibility of erasing/rewriting the fabricated patterns through multiple annealing/hydrogenation procedures, the inherently precise control over the position of the nanostructures fabricated with this method renders them naturally suited for the integration with photonic crystal nanocavities.