Suchergebnisse

Quaternary alloys enable the independent optimization of different semiconductor properties, such as the separate tuning of the band gap and the lattice constant. Nanowire core-shell structures should allow a larger range of compositional tuning as strain can be accommodated in a more effective manner than in thin films. Still, the faceted structure of the nanowire may lead to local segregation effects. Here, we explore the incorporation of indium in AlGaAs shells up to 25%. In particular, we show the effect of In incorporation on the energy shift of the AlGaInAs single-photon emitters present in the shell. We observe a redshift up to 300 meV as a function of the group-III site fraction of In. We correlate the shift with segregation at the nanoscale. We find evidence of the segregation of the group-III elements at different positions in the nanowire, not observed before. We propose a model that takes into account the strain distribution in the nanowire shell and the adatom diffusion on the nanowire facets to explain the observations. This work provides novel insights on the segregation phenomena necessary to engineer the composition of multidinary alloys. ; JSR thanks the European H2020 for funding through grant LIMQUET. EDR and LR thank Labex EMC3 AQURATE (French ANR). SMS acknowledges funding from "Programa Internacional de Becas 'la Caixa'-Severo Ochoa." JA and SMS acknowledge funding from Generalitat de Catalunya 2017 SGR 327 and the Spanish MINECO project ENE2017-85087-C3. ICN2 acknowledges support from the Severo Ochoa Programme (MINECO, Grant No. SEV-2013-0295) and is funded by the CERCA Programme / Generalitat de Catalunya. Part of the present work has been performed in the framework of Universitat Autònoma de Barcelona Materials Science PhD program. This work has received funding from the European Union's Horizon 2020 Research and Innovation Programme under grant agreement No. 654360 NFFA-Europe. ; Peer reviewed

8 figures.-- Supplementary information available. ; The controlled modification of the electronic properties of ZnO nanorods via transition metal doping is reported. A series of ZnO nanorods were synthesized by chemical bath growth with varying Co content from 0 to 20 atomic % in the growth solution. Optoelectronic behavior was probed using cathodoluminescence, time-resolved luminescence, transient absorbance spectroscopy, and the incident photon-to-current conversion efficiency (IPCE). Analysis indicates the crucial role of surface defects in determining the electronic behavior. Significantly, Co-doping extends the light absorption of the nanorods into the visible region, increases the surface defects, shortens the non-radiative lifetimes, while leaving the radiative lifetime constant. Furthermore, for 1 atomic % Co-doping the IPCE of the ZnO nanorods is enhanced. These results demonstrate that doping can controllably tune the functional electronic properties of ZnO nanorods for applications. ; This work has received funding from the Horizon 2020 program of the European Union for research and innovation, under grant agreement no. 722176 (INDEED) and SNSF via project nr-40B2-0_176680 and BSCGI0-157705. WKM, AMB acknowledge Spanish MINEICO under project ENE2016-79282-C5-1-R (AEI/FEDER, UE) and Gobierno de Aragón (Grupo Reconocido DGAT03_17R (FEDER, UE and T03_20R). ; Peer reviewed