Resonant tunneling of electrons via 20 nm scale InAs quantum dot and magnetotunneling spectroscopy of its electronic states

Narihiro, M.; Yusa, Go; Nakamura, Y.; Noda, Takeshi; Sakaki, H.

doi:10.1063/1.119276

Cited by 126 publications

(70 citation statements)

References 11 publications

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“…8,9,17,18 We attribute this to the fact that the energy levels of the QD ground states lie below the chemical potential in the emitter at all biases so energy-conserving tunneling transitions through the dots are not allowed.…”

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confidence: 99%

Excited states of ring-shaped (InGa)As quantum dots in aGaAs∕(AlGa)Asquantum well

et al. 2005

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By studying the resonant tunneling of electrons through self-assembled ring-shaped ͑InGa͒As quantum dots embedded in the quantum well of an ͑AlGa͒As/ GaAs/ ͑AlGa͒As heterostructure, we find evidence for the existence of excited states of the quantum dots which exhibit a 2p z -like character along the growth direction z. The states are investigated by magnetotunneling spectroscopy with magnetic fields applied parallel and perpendicular to z. DOI: 10.1103/PhysRevB.72.085309 PACS number͑s͒: 73.23.Ϫb, 73.63.Kv, 73.40.Gk In self-assembled semiconductor quantum dots ͑QDs͒, carriers are confined in all three spatial dimensions. This leads to a spectrum of discrete energy levels, similar to that of atoms. [1][2][3][4][5][6][7] The analogy with atoms is strengthened by the observation of excitonic and electronic states with s-, p-, and d-like character, all of which have been observed in optical 6 and tunneling 8,9 spectroscopy studies. In addition, optical pumping experiments have provided evidence for shell-like filling of the electronic orbitals. 6 However, in contrast to a real atom, a QD has a highly anisotropic confining potential, since its dimensions in the plane of growth ͑the wetting layer plane x-y͒ are typically an order of magnitude larger than that along the growth direction ͑z͒. Hence spectroscopic investigations have been restricted mainly to states for which the excitations are confined to the x-y plane.In this paper, we study the electronic properties of QDs with an unusual ring-shape morphology, which can be generated under special growth conditions. We report experimental evidence for the presence of excited QD states with a 2p z -like character. States with 2p z character have been observed previously for Si donors in a GaAs QW.10 For this study we use resonant tunneling heterostructure diodes in which a single layer of self-assembled ͑InGa͒As quantum dots is embedded in an ͑AlGa͒As/ GaAs/ ͑AlGa͒As quantum well. The 2p z -like quasibound states are revealed by the presence of additional resonant peaks in the tunnel current. By combining photoluminescence and magnetotunneling spectroscopy with magnetic field B applied along z and in the x-y plane, we show that these resonances correspond to electron tunneling into 2p z -like states with binding energies in the range 5 -30 meV below the edge of the continuum of the first excited two-dimensional ͑2D͒ subband of the GaAs QW.Despite the ring-shape structure of the dots, we find no evidence in our tunneling data for states showing AharonovBohm character.Our device is a GaAs/ Al 0.4 Ga 0.6 As double barrier electron resonant tunneling diode ͑RTD͒ grown by molecular beam epitaxy ͑MBE͒ on a ͑100͒-oriented n + GaAs substrate. The conduction band profile of the device and the QD energy levels are shown schematically in Fig. 1͑a͒. Two 8-nm-thick Al 0.4 Ga 0.6 As tunnel barriers define a 10-nm-thick GaAs QW, which contains a layer of ͑InGa͒As QDs. Undoped GaAs spacer layers of width 50 nm separate the Al 0.4 Ga 0.6 As barriers from lightly n-doped ͑n =2ϫ 10 1...

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Excited states of ring-shaped (InGa)As quantum dots in aGaAs∕(AlGa)Asquantum well

et al. 2005

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“…Similar features are observable in resonant tunneling diodes with an embedded QD layer [15][16][17]. Here the inhomogeneity of the QD size distribution in connection with Coulomb charging can provide negative differential conductivity [18].…”

Section: Coulomb Interaction Within a Quantum Dot Layermentioning

confidence: 52%

Theory of Nonlinear Transport for Ensembles of Quantum Dots

Kießlich¹,

Wacker²,

Schöll³

2008

Semiconductor Nanostructures

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“…A schematic band diagram of our device is shown in Figure 1a (see ref.14 for a detailed description of the device composition). A twodimensional InAs wetting layer (WL) on the collector side of the barrier produces a depletion layer in close proximity to the InAs QDs, thus facilitating electron tunneling from the dots through the continuum states of the WL and finally into the n-doped GaAs collector contact, see 6 for a 25 µm diameter mesa), only a small number of narrow peaks can be typically observed in the low bias (< 0.1V) current-voltage curves, I(V ) 4, 5,6,7 . This behaviour is associated with a limited number of tunneling channels that can efficiently transmit electrons in this low bias range.…”

Section: Devices and Experimental Datamentioning

confidence: 99%

“…Semiconducting quantum dots (QDs), formed by lithographic processing or by self-assembly, have proved to be versatile nanostructures for studying and exploiting resonant electron tunneling through a single, discrete quantum state 1,2,3,4, 5,6 . Usually, the resonance condition is achieved by tuning the voltage applied either to a twoterminal diode 4, 5,6,7 or else to a gate electrode of a transistor structure 1,2,3,7 .…”

Section: Introductionmentioning

confidence: 99%

“…Usually, the resonance condition is achieved by tuning the voltage applied either to a twoterminal diode 4, 5,6,7 or else to a gate electrode of a transistor structure 1,2,3,7 . The electrostatic potential arising from charges on a surface gate tends to have only a gradual spatial variation, given by Poisson's equation and characterized by a length scale that is large compared to the typical size (∼ 10 nm) of a QD.…”

Section: Introductionmentioning

confidence: 99%

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Sensitive detection of photoexcited carriers by resonant tunneling through a single quantum dot

et al. 2009

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We show that the resonant tunnel current through a single energy level of an individual quantum dot within an ensemble of dots is strongly sensitive to photoexcited holes that become bound in the close vicinity of the dot. The presence of these holes lowers the electrostatic energy of the quantum dot state and switches the current carrying channel from fully open to fully closed with a high on/off ratio (> 50). The device can be reset by means of a bias voltage pulse. These properties are of interest for charge sensitive photon counting devices.

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Resonant tunneling of electrons via 20 nm scale InAs quantum dot and magnetotunneling spectroscopy of its electronic states

Cited by 126 publications

References 11 publications

Excited states of ring-shaped (InGa)As quantum dots in aGaAs∕(AlGa)Asquantum well

Excited states of ring-shaped (InGa)As quantum dots in aGaAs∕(AlGa)Asquantum well

Theory of Nonlinear Transport for Ensembles of Quantum Dots

Sensitive detection of photoexcited carriers by resonant tunneling through a single quantum dot

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