Terahertz generation in ordered arrays of GaAs nanowires

THz generation under excitation by ultrashort optical pulses from ordered arrays of GaAs nanowires is reported. It was found that the efficiency of THz generation process is determined by the excitation of leaky modes for the light incident on the semiconductor nanocrystal and increases due to the resonant excitation of Mie modes. Furthermore, it is shown that the efficiency of the terahertz generation at optimum geometrical parameters of an array of semiconductor nanowires is greater than the corresponding value for bulk semiconductor p-InAs which is the most effective THz emitter

Sharp emission from single InAs quantum dots grown on vicinal GaAs surfaces

We report on optical studies of single InAs quantum dots grown on vicinal GaAs(001) surfaces. To ensure low quantum dot density and appropriate size, we deposit InAs layers 1.4 or 1.5 ML thick, thinner than the critical thickness for Stranski–Krastanov quantum dot formation. These dots show sharp and bright photoluminescence. Lifetime measurements reveal an exciton lifetime of 500 ps. Polarization measurements show an exciton fine structure splitting of 15??eV and allow to identify the exciton and charged exciton transitions with linewidth as narrow as 23??eV.Kavli Institute of NanoscienceApplied Science

Self-catalyzed, pure zincblende GaAs nanowires grown on Si(111) by molecular beam epitaxy.

We report on the Au-free molecular beam epitaxy growth of coherent GaAs nanowires directly on Si(111) substrates. The growth is catalyzed by liquid Ga droplets formed in the openings of a native oxide layer at the initial growth stage. Transmission electron microscopy studies demonstrate that the nanowires are single crystals having the zincblende structure along their length (apart from a thin wurtzite region directly below the Ga droplet), regardless of their diameter (70–80 nm) and the growth temperature range (560–630 °C). We attribute the observed phase purity to a much lower surface energy of liquid Ga than that of Au-Ga alloys, which makes triple line nucleation energetically unfavorable. The change in growth catalyst to a liquid metal with a lower energy suppresses the (more usual) formation of wurtzite nuclei on surface energetic grounds. These results can provide a distinct method for the fabrication of chemically pure and stacking-fault-free zincblende nanowires of III-V compounds on silicon