Towards scalable gated quantum dots for quantum information applications

Reimer, Michael E.; McKinnon, W. R.; Lapointe, J.; Dalacu, Dan; Poole, Philip J.; Aers, G. C.; Kim, D.; Korkusiński, Marek; Hawrylak, Paweł; Williams, Robin L.

doi:10.1016/j.physe.2007.08.131

Cited by 20 publications

(18 citation statements)

References 13 publications

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“…A single quantum dot in a pyramidal nanotemplate forms an ideal geometry for devices requiring metal gates for application of electric fields and optical access for PL spectroscopy. Vertical fields can be applied across the intrinsic region of the pyramid using Au/Ti Schottky gates on the sidewalls of the pyramid and an n-doped substrate serving as a back con-tact [41,63]. An SEM image of a typical device is shown in the title figure where gates have been deposited on each of the four f110g sidewalls of the pyramid.…”

Section: Optical Spectroscopymentioning

confidence: 99%

“…The two emission lines from the X 2 relaxation is a consequence of two possible final states with parallel or anti-parallel spin orientations of the two remaining electrons and the concomitant difference in s-p exchange energies [54,61,64]. The specific carrier occupation of the dot at each bias is a consequence of the particular geometry of the device together with the substrate doping and background carrier concentration in the pyramid [63]. As well as single electron charging, an applied bias redshifts the energies of the exciton complexes due to the quantum confined Stark effect [65].…”

Section: Optical Spectroscopymentioning

confidence: 99%

“…9 shows the emission energies of X and X as a function of applied field, with an offset added to X assuming a negligible reduction in dipole due to the additional electron [60]. The field is calculated by simultaneously solving Poisson's equation and the continuity equations for electrons and holes, whilst utilizing the drift diffusion model for charge transport [63].…”

Section: Optical Spectroscopymentioning

confidence: 99%

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Directed self‐assembly of single quantum dots for telecommunication wavelength optical devices

Dalacu¹,

Reimer

Frédérick

et al. 2010

Laser & Photonics Reviews

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Strong confinement of charges in few electron systems such as in atoms, molecules and quantum dots leads to a spectrum of discrete energy levels that are often shared by several degenerate quantum states. Since the electronic structure is key to understanding their chemical properties, methods that probe these energy levels in situ are important. We show how electrostatic force detection using atomic force microscopy reveals the electronic structure of individual and coupled self-assembled quantum dots. An electron addition spectrum in the Coulomb blockade regime, resulting from a change in cantilever resonance frequency and dissipation during tunneling events, shows one by one electron charging of a dot. The spectra show clear level degeneracies in isolated quantum dots, supported by the first observation of predicted temperature-dependent shifts of Coulomb blockade peaks. Further, by scanning the surface we observe that several quantum dots may reside on what topologically appears to be just one. These images of grouped weakly and strongly coupled dots allow us to estimate their relative coupling strengths.

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Section: Optical Spectroscopymentioning

confidence: 99%

Section: Optical Spectroscopymentioning

confidence: 99%

Section: Optical Spectroscopymentioning

confidence: 99%

See 1 more Smart Citation

Directed self‐assembly of single quantum dots for telecommunication wavelength optical devices

Dalacu¹,

Reimer

Frédérick

et al. 2010

Laser & Photonics Reviews

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“…In this regime, the exciton wave function can be directly modified, leading to energy shifts, carrier tunneling, and fine-structure splitting reduction, among other effects. [15][16][17][18][19] With a channel width of only 1.5 µm, our MSM diodes have been designed to apply large electric fields in the [110] crystal direction (0−60 kV/cm). This is required to tune independently the exciton energy of the two QDs in a lateral molecule and, if their separation were small enough, to observe resonant quantum tunneling phenomena.…”

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confidence: 99%

Charge control in laterally coupled double quantum dots

et al. 2011

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We investigate the electronic and optical properties of InAs double quantum dots grown on GaAs (001) and laterally aligned along the [110] crystal direction. The emission spectrum has been investigated as a function of a lateral electric field applied along the quantum dot pair mutual axis. The number of confined electrons can be controlled with the external bias, leading to sharp energy shifts which we use to identify the emission from neutral and charged exciton complexes. Quantum tunneling of these electrons is proposed to explain the reversed ordering of the trion emission lines as compared to that of excitons in our system. Optical spin initialization of individual electrons is a fundamental resource for quantum information science which relies on our ability to control the charge in a quantum dot (QD) molecule. [1][2][3] In the past, vertically aligned QDs have been fabricated with great success. In these systems, exciton coupling signatures including energy anticrossings of neutral and charged exciton complexes, have been demonstrated by applying an electric field in the growth direction.4-6 Lateral QD molecules would be a better candidate for scaling up the electronic coupling from two to several QDs by applying individual lateral gates. Previous demonstrations of electronic coupling in a lateral QD pair have been based on an analysis of the anomalous Stark shifts and photon correlation statistics of the neutral exciton under a lateral electric field.7 Yet, the observation of electrically tunable energy anticrossings in lateral QD molecules remains a difficult task due to the exponential decrease of the tunnel coupling energy with the center-to-center QD distance d. [7][8][9] In the following, we investigate the emission spectrum of electrically tunable lateral QD pairs with a varying number of electrons. For typical interdot distances d ∼ 30-40 nm, we find that electron tunneling phenomena affect the negative trion emission energy before clear exciton anticrossings may take place.For the present study, QD pairs aligned in the [110] crystal direction were fabricated on GaAs nanoholes using a modified droplet epitaxy growth procedure as described in detail elsewhere. 10 The nanostructures were grown on a 0.5-µm-thick undoped GaAs buffer layer and capped by 100 nm of undoped GaAs. Atomic force micrographs (AFMs) performed on a similar uncapped sample revealed that each QD in the pair has a slightly different height, with average values of 5.3 ± 0.9 and 6.6 ± 1.5 nm, respectively, and centerto-center separation equal to their average diameter 37 ± 4 nm [ Fig. 1(a)]. The morphological analysis also revealed that QD pair formation occurs in 95% of the cases with a small probability for single QDs or empty nanoholes. The low areal density of 2 × 10 8 cm −2 is adequate to study individual quantum nanostructures.To apply an electric field along the QD pair mutual axis, we defined metal-semiconductor-metal (MSM) diodes by evaporation of two metal contacts (15 nm Mo + 30 nm Au) on top of 100-µm-square mesas. The ...

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“…4(c)]. 32 Clearly, although the net electric charge can be varied in different QDh, its precise value can not be set in each one independently. This limitation, imposed by the size inhomogeneity inherent in self-assembled growth methods, 4 could be solved in the future using individual gating technologies.…”

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confidence: 99%

Electrical control of a laterally ordered InAs/InP quantum dash array

et al. 2009

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We have fabricated an array of closely spaced quantum dashes starting from a planar array of self-assembled semiconductor quantum wires. The array is embedded in a metallic nanogap which we investigate by micro-photoluminescence as a function of a lateral electric field. We demonstrate that the net electric charge and emission energy of individual quantum dashes can be modified externally with performance limited by the size inhomogeneity of the self-assembling process.

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Towards scalable gated quantum dots for quantum information applications

Cited by 20 publications

References 13 publications

Directed self‐assembly of single quantum dots for telecommunication wavelength optical devices

Directed self‐assembly of single quantum dots for telecommunication wavelength optical devices

Charge control in laterally coupled double quantum dots

Electrical control of a laterally ordered InAs/InP quantum dash array

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