Quantum dots in the GaAs/AlxGa1−xAs core-shell nanowires: Statistical occurrence as a function of the shell thickness

Abstract

Quantum dots (QDs) embedded in nanowires represent one of the most promising technologies for applications in quantum photonics. Self-assembled bottom-up fabrication is attractive to overcome the technological challenges involved in a top-down approach, but it needs post-growth investigations in order to understand the self-organization process. We investigate the QD formation by selfsegregation in Al x Ga 1Àx As shells as a function of thickness and cross-section morphology. By analysing light emission from several hundreds of emitters, we find that there is a certain thickness threshold for the observation of the QDs. The threshold becomes smaller if a thin AlAs layer is pre-deposited between the GaAs nanowire core and the Al x Ga 1Àx As shell. Our results evidence the development of the quantum emitters during the shell growth and provide more guidance for their use in quantum photonics. V C 2015 AIP Publishing LLC. [http://dx

Exciton dynamics in GaAs/(Al,Ga)As core-shell nanowires with shell quantum dots

“…23 A statistical analysis of the PL spectra of 100 nanowires (not shown) reveals that each nanowire contains on average 13 optically active shell QDs per nanowire. However, as QDs located in the innermost 20 nm of the shells 21 and at the surface do not contribute to the PL spectrum, it is likely that the total number of shell QDs in our nanowires is much larger. Figure 3(b) shows the evolution with excitation power of the PL at 10 K from a shell QD emitting at 1.7504 eV.…”

Tuning adatom mobility and nanoscale segregation by twin formation and polytypism

“…(a) Simplified 3D representation and cross-sectional sketch of the core-shell GaAs-AlGaAs NW structure. The possible Ga-rich emitters are depicted in red and orange in the shell, depicted in blue [26][27][28]. (b) On the left: contour plot of normalized PL spectra in the 1.72 -1.90 eV energy range from the bottom to the top of a NW on a TEM grid (1 μm steps between consequent spectra).…”

“…On the right: PL spectra (not normalized) from the positions indicated by the dashed vertical lines in the contour plot. extensively reported to be spatially non-uniform, with Al-rich planes at the ridge between two NW facets [26][27][28]33]. By changing the deposition time of the AlGaAs shell we grew three different samples with nominal shell thickness of 30 , 50 , and 100 nm.…”

“…It has been shown that AlGaAs exhibits spontaneous segregation of Al and Ga at the nanoscale. Ga-rich clusters can form [26,27] and act as QDlike single-photon emitters in the 1.72-1.90 eV emission range [26,28]. While the exact formation mechanism for these QDs is still unknown, the differentiated adatom mobility in the facets and corners of the NW core is one of the key elements in the explanation.…”

Diamagnetic susceptibility of the electron gas in the cylindrical nanolayer

“…In these studies, the possibility to control the thermodynamic and magnetic properties of the electron gas by way of changing the geometric parameters of the QD was demonstrated. In this regard, it should be noted that in recent years the attention is greatly increased to the QD with the layered geometry: quantum rings, spherical and cylindrical systems (core/shell/shell) [13][14][15][16][17][18]. In such structures, the manipulation of the electron energy levels can be done by changing the external and internal radii.…”