Crystal structure and optical characterization of heterostructured GaAs/AlGaAs/GaAs nanowires

Abstract

Structural and optical properties of heterostructured GaAs/AlGaAs/GaAs core/inner shell/outer shell nanowires are studied. Transmission electron microscopy and Raman scattering measurements unambiguously identify the presence of segments crystallized in zincblende and wurtzite phases, which spread to the shells. Four observed photoluminescence lines are assigned to the radiative recombination of photoexcited electrons confined in the center of the GaAs core and at the heterointerface between the outer GaAs shell and the inner AlGaAs shell with the holes localized at the heterointerface between the core and the inner AlGaAs shell; both recombinations take place in zincblende and wurtzite phases. One additional photoluminescence line is attributed to the spatially indirect recombination between the electrons in zincblende and the holes in wurtzite phases. The bandgap of the wurtzite phase and the band offsets between the zincblende and wurtzite phases are determined.

Manipulation of emission energy in GaAs/AlGaAs core-shell nanowires with radial heterostructure

“…2. Basing on our earlier studies, [17][18][19] two PL lines (PL1 and PL2) observed in the undoped NWs with the outer shell formed by a GaAs layer were attributed to the recombination between the photoexcited electrons and holes in the GaAs core and between the photoexcited carriers confined in the range of the inner shell, respectively. The presented identification of the PL lines was supported by corresponding modifications of the PL1 and PL2 emissions observed in NWs with different inner shell/outer shell structures and by their temperature and temporal dependences.…”

“…Moreover, high-resolution transmission electron microscopy (TEM), Raman scattering of lattice vibrations and PL measurements demonstrated formation of segments of crystallized in zincblende and wurtzite phases. It was shown that the PL is dominated by the emission from zincblende phase, 18 which is a subject of this study.…”

“…An energy-dispersive x-ray spectroscopy (EDS) structural analysis performed in Ref. 18 in core-inner shell-outer shell GaAs/Al 0.3 Ga 0.7 As/GaAs NWs, with the inner shell grown equivalently to a planar growth of 90 nm thick Al 0.3 Ga 0.7 As s layer, definitely showed a presence of Al in the inner shell. Roughly, the thickness of the Al 0.3 Ga 0.7 As inner shell was estimated as equal to 5-10 monolayers.…”

“…As a consequence of such charge separation, the probability of radiative recombination decreases. In our recently published articles, [17][18][19] where we studied optical properties of radial heterostructure core/inner shell/outer shell GaAs/AlGaAs/GaAs NWs, we demonstrated that a thin potential barrier produced by the inner AlGaAs shell causes accumulation of the photoexcited electrons and holes in vicinity of the barrier. In such a case, the electrons are confined at the heteroboundary between the outer GaAs shell and the inner AlGaAs one, while the holes reside in the GaAs core.…”

Processos ópticos em semicondutores híbridos formados por nanofios heteroestruturados de AlGaAs/GaAs e polímero conjugado com potencial aplicação em dispositivos fotovoltaicos

“…* evaporar o As, em geral, era insuficiente para evaporar o Ga em um crescimento estequiométrico. (11,23,31) O aperfeiçoamento da técnica de crescimento a partir da evaporação de grupos III e V fora desenvolvidas por Günther (35). Neste método os feixes dos grupos III e V eram obtidos a partir de amostras individuais de seus compostos puros, assim o crescimento do GaAs, como exemplo, as carga (quantidade do material) de As eram mantidas a uma temperatura T 1 , a carga de Ga mantida em T 2 , e com uma temperatura intermediaria para o substrato com esta divisão gerava uma maior eficiência para obter a razão do fluxo de V/III mais efetivo para o crescimento, este método ficou conhecido como método das três temperaturas.…”