Magneto-optical properties of single site-controlled ingaasn quantum wires grown on prepatterned gaas substrates

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Excitonic recombination and absorption in InxGa1-xAs/GaAs heterostructure nanowires

Photoluminescence (PL), micro-PL, and PL excitation (PLE) spectroscopy for different light polarizations have been used to investigate the electronic properties of GaAs characterized by a dominant wurtzite (WZ) phase that forms in bare GaAs and in InGaAs/GaAs heterostructure (HS) nanowires (NWs). In both cases, the GaAs luminescence exhibits very narrow emission lines, which persist up to room temperature. At 10 K, the energy of the exciton ground state recombination of GaAs NWs is equal to 1.522-1.524 eV. In HS NWs, micro-PL combined with transmission electron microscopy pinpoints the tip of the GaAs section, with a dominant WZ phase, as the origin of that emission. In PLE, two very narrow excitonic absorptions at 1.523 and 1.631 eV involve different critical points of the WZ valence band (Gamma(9 nu) and Gamma(7 nu mu)). The low-energy peak shows a negligible Stokes shift with respect to PL. At 10 K, a further weak and broad PLE signal is found at 1.59 eV. The possible attribution of these lines within the present knowledge of the WZ band structure is critically discussed

Effects of hydrogen irradiation on the optical and electronic properties of site-controlled InGaAsN V-groove quantum wires

The properties of InGaAsN V-groove QWRs are assessed here by polarization-dependent photoluminescence (PL) and micro-magneto-PL. Both the polarization anisotropy of the QWR emission and the strong dependence of the diamagnetic shift on the orientation of the applied magnetic field confirm the 1D nature of the QWR excitons. Further, the possibility of passivating N impurities by H irradiation is used to estimate the N content (x) in the QWRs by turning off the effects of N incorporation. Both the H-induced blueshift of the QWR emission (70 meV) and the measured value of the electron effective mass are consistent with x ∼1%. Nitrogen is also found to enhance the In intake in the QWR, likely due to the strain reduction resulting from the smaller lattice parameter of the InGaAsN alloy. Such strain reduction is also responsible for the quick decay of the degree of linear polarization (ρ) of the QWR emission with increasing temperature, indicating a small splitting between the QWR valence-band levels. In fully hydrogenated samples, conversely, ρ remains roughly constant up to ∼240 K, suggesting the recovery of a larger energy separation between the QWR hole states upon N passivation