Effects of random alloy disorder, shape deformation, and substrate misorientation on the exciton lifetime and fine structure splitting of GaAs/AlxGa1-xAs(111) quantum dots

Using atomistic, million-atom screened pseudopotential theory together with configuration interaction, as well as atomically resolved structures based on experimental characterization, we perform numerical calculations on self-assembled GaAs/AlxGa1-xAs(111) quantum dots that we compare with our experimental data. We show that random alloy disorder in the barrier can cause a symmetry breaking at the single-particle level (distortions of wave functions and lifting of degeneracies) which translates into the appearance of a nonzero exciton fine structure splitting (FSS) at the many-body level. Nevertheless, our results indicate that varying the concentration of aluminum in the random alloyed barrier allows simultaneous tuning of the exciton fine structure splitting and emission wavelength without altering its radiative lifetime tau approximate to 200 ps. Additionally, the optical properties of these quantum dots are predicted to be very robust against both symmetric and asymmetric shape elongation (with FSS 2.2 mu eV), rendering postselection less essential under well-controlled growth conditions. On the other hand, the growth on miscut substrates introduces a structural anisotropy along the quantization axis to which the system is very sensitive: the FSS ranges between 5 and 50 mu eV while the radiative lifetime of the transition is increased up to tau = 400 ps. The numerical results for the FSS are in perfect agreement with our experimental measurements which give FSS = 10 +/- 9 mu eV for 2 degrees miscut angle at x = 0.15

Photoluminescence Study of Low Thermal Budget III–V Nanostructures on Silicon by Droplet Epitaxy

We present of a detailed photoluminescence characterization of high efficiency GaAs/AlGaAs quantum nanostructures grown on silicon substrates. The whole process of formation of the GaAs/AlGaAs active layer was realized via droplet epitaxy and migration enhanced epitaxy maintaining the growth temperature ≤350°C, thus resulting in a low thermal budget procedure compatible with back-end integration of the fabricated materials on integrated circuits

Wurtzite nanowires strain control by DC electrical stimulation

Nanomechanics is a highly developed area of research, given the significant reported changes in material properties at the nanometer scale, requiring the development of new theories to explain the underlying mechanisms. Such theories must be based on measurements that are as accurate as possible, but unfortunately, conventional experimental techniques do not apply to such small components. Here we present a unique new method to control electro-mechanical forces on quasi −1D nanostructures through static electric fields with multiple ways of control of GaAs nanowires’ strain directly on the growth substrate

Electroproduction, photoproduction, and inverse electroproduction of pions in the first resonance region

Methods are set forth for determining the hadron electromagnetic structure in the sub-$N\bar{N}$-threshold timelike region of the virtual-photon ``mass'' and for investigating the nucleon weak structure in the spacelike region from experimental data on the process $\pi N\to e^+e^- N$ at low energies. These methods are formulated using the unified description of photoproduction, electroproduction, and inverse electroproduction of pions in the first resonance region in the framework of the dispersion-relation model and on the basis of the model-independent properties of inverse electroproduction. Applications of these methods are also shown.Comment: The revised published version; Revtex4, 18 pages, 6 figure

Multiexciton complex from extrinsic centers in AlGaAs epilayers on Ge and Si substrates

The multiexciton properties of extrinsic centers from AlGaAs layers on Ge and Si substrates are addressed. The two photon cascade is found both in steady state and in time resolved experiments. Polarization analysis of the photoluminescence provides clearcut attribution to neutral biexciton complexes. Our findings demonstrate the prospect of exploiting extrinsic centers for generating entangled photon pairs on a Si based device.Sarti, F.; Muñoz Matutano, G.; Bauer, D.; Dotti, N.; Bietti, S.; Isella, G.; Vinattieri, A.... (2013). Multiexciton complex from extrinsic centers in AlGaAs epilayers on Ge and Si substrates. Journal of Applied Physics. 114(22):2243141-2243143. doi:10.1063/1.4844375S2243141224314311422Kimble, H. J. (2008). The quantum internet. Nature, 453(7198), 1023-1030. doi:10.1038/nature07127Bouwmeester, D., Pan, J.-W., Mattle, K., Eibl, M., Weinfurter, H., & Zeilinger, A. (1997). Experimental quantum teleportation. Nature, 390(6660), 575-579. doi:10.1038/37539Shields, A. J. (2007). Semiconductor quantum light sources. Nature Photonics, 1(4), 215-223. doi:10.1038/nphoton.2007.46Akopian, N., Lindner, N. H., Poem, E., Berlatzky, Y., Avron, J., Gershoni, D., … Petroff, P. M. (2006). Entangled Photon Pairs from Semiconductor Quantum Dots. Physical Review Letters, 96(13). doi:10.1103/physrevlett.96.130501Dousse, A., Suffczyński, J., Beveratos, A., Krebs, O., Lemaître, A., Sagnes, I., … Senellart, P. (2010). Ultrabright source of entangled photon pairs. Nature, 466(7303), 217-220. doi:10.1038/nature09148Cavigli, L., Bietti, S., Accanto, N., Minari, S., Abbarchi, M., Isella, G., … Sanguinetti, S. (2012). High temperature single photon emitter monolithically integrated on silicon. Applied Physics Letters, 100(23), 231112. doi:10.1063/1.4726189Accanto, N., Minari, S., Cavigli, L., Bietti, S., Isella, G., Vinattieri, A., … Gurioli, M. (2013). Kinetics of multiexciton complex in GaAs quantum dots on Si. Applied Physics Letters, 102(5), 053109. doi:10.1063/1.4790148Kurtsiefer, C., Mayer, S., Zarda, P., & Weinfurter, H. (2000). Stable Solid-State Source of Single Photons. Physical Review Letters, 85(2), 290-293. doi:10.1103/physrevlett.85.290Brouri, R., Beveratos, A., Poizat, J.-P., & Grangier, P. (2000). Photon antibunching in the fluorescence of individual color centers in diamond. Optics Letters, 25(17), 1294. doi:10.1364/ol.25.001294Strauf, S., Michler, P., Klude, M., Hommel, D., Bacher, G., & Forchel, A. (2002). Quantum Optical Studies on Individual Acceptor Bound Excitons in a Semiconductor. Physical Review Letters, 89(17). doi:10.1103/physrevlett.89.177403Muller, A., Bianucci, P., Piermarocchi, C., Fornari, M., Robin, I. C., André, R., & Shih, C. K. (2006). Time-resolved photoluminescence spectroscopy of individual Te impurity centers inZnSe. Physical Review B, 73(8). doi:10.1103/physrevb.73.081306Sanaka, K., Pawlis, A., Ladd, T. D., Sleiter, D. J., Lischka, K., & Yamamoto, Y. (2012). Entangling Single Photons from Independently Tuned Semiconductor Nanoemitters. Nano Letters, 12(9), 4611-4616. doi:10.1021/nl301911tIkezawa, M., Sakuma, Y., Zhang, L., Sone, Y., Mori, T., Hamano, T., … Masumoto, Y. (2012). Single-photon generation from a nitrogen impurity center in GaAs. Applied Physics Letters, 100(4), 042106. doi:10.1063/1.3679181Minari, S., Cavigli, L., Sarti, F., Abbarchi, M., Accanto, N., Muñoz Matutano, G., … Gurioli, M. (2012). Single photon emission from impurity centers in AlGaAs epilayers on Ge and Si substrates. Applied Physics Letters, 101(17), 172105. doi:10.1063/1.4761939Marcet, S., Ouellet-Plamondon, C., Éthier-Majcher, G., Saint-Jean, P., André, R., Klem, J. F., & Francoeur, S. (2010). Charged excitons and biexcitons bound to isoelectronic centers. Physical Review B, 82(23). doi:10.1103/physrevb.82.235311Jo, M., Mano, T., Kuroda, T., Sakuma, Y., & Sakoda, K. (2013). Visible single-photon emission from a nitrogen impurity center in AlAs. Applied Physics Letters, 102(6), 062107. doi:10.1063/1.4792315Abbarchi, M., Mastrandrea, C., Kuroda, T., Mano, T., Vinattieri, A., Sakoda, K., & Gurioli, M. (2009). Poissonian statistics of excitonic complexes in quantum dots. Journal of Applied Physics, 106(5), 053504. doi:10.1063/1.3197848Kuroda, T., Sanguinetti, S., Gurioli, M., Watanabe, K., Minami, F., & Koguchi, N. (2002). Picosecond nonlinear relaxation of photoinjected carriers in a singleGaAs/Al0.3Ga0.7Asquantum dot. Physical Review B, 66(12). doi:10.1103/physrevb.66.121302Gammon, D., Snow, E. S., Shanabrook, B. V., Katzer, D. S., & Park, D. (1996). Fine Structure Splitting in the Optical Spectra of Single GaAs Quantum Dots. Physical Review Letters, 76(16), 3005-3008. doi:10.1103/physrevlett.76.3005Abbarchi, M., Mastrandrea, C. A., Kuroda, T., Mano, T., Sakoda, K., Koguchi, N., … Gurioli, M. (2008). Exciton fine structure in strain-freeGaAs/Al0.3Ga0.7Asquantum dots: Extrinsic effects. Physical Review B, 78(12). doi:10.1103/physrevb.78.125321Heiss, M., Fontana, Y., Gustafsson, A., Wüst, G., Magen, C., O’Regan, D. D., … Fontcuberta i Morral, A. (2013). Self-assembled quantum dots in a nanowire system for quantum photonics. Nature Materials, 12(5), 439-444. doi:10.1038/nmat355