Selective Area Sublimation: A Simple Top-down Route for GaN-Based Nanowire Fabrication.

Post-growth in situ partial SiNx masking of GaN-based epitaxial layers grown in a molecular beam epitaxy reactor is used to get GaN selective area sublimation (SAS) by high temperature annealing. Using this top-down approach, nanowires (NWs) with nanometer scale diameter are obtained from GaN and InxGa1-xN/GaN quantum well epitaxial structures. After GaN regrowth on InxGa1-xN/GaN NWs resulting from SAS, InxGa1-xN quantum disks (QDisks) with nanometer sizes in the three dimensions are formed. Low temperature microphotoluminescence experiments demonstrate QDisk multilines photon emission around 3 eV with individual line widths of 1-2 meV.

Optical and structural properties of an Eu implanted gallium nitride quantum dots/aluminium nitride superlattice.

GaN/AIN structures made of GaN quantum dots (QDs) separated by AIN spacer layers, were doped with Europium by ion implantation. Rutherford Backscattering/Channelling measurements showed that Eu is incorporated mainly on near-substitutional cation sites within the superlattice region. Only slight deterioration of the crystal quality and no intermixing of the different layers are observed after implantation and annealing. After thermal annealing, photoluminescence associated with Eu3+ ions was observed. From its behaviour under different photon energy excitation and sample temperature we concluded that the Eu-related emitting centres are located inside the GaN QDs or dispersed in the GaN and AIN buffer or spacer layers. The 624 nm PL line, associated with Eu-doped GaN QDs, shows very low thermal quenching, suggesting recombination of confined carriers through rare-earth ion excitation.

Photoluminescence properties of multiple stacked planes of GaN/AlN quantum dots studied by near-field optical microscopy.

We have studied the photoluminescence properties of GaN quantum dots with submicrometre lateral resolution by means of near-field scanning optical microscopy. The instrument operated at room temperature and was implemented for near-ultra-violet spectroscopy in the illumination-mode configuration. The analysed sample consisted of several stacked planes of GaN/AlN quantum dots grown by molecular beam epitaxy on Si(111) substrate. The photoluminescence maps showed islands in the micrometre range emitting at different wavelengths, confirming the atomic force microscopy studies on the morphology of similar uncapped samples.