Single-electron charging of self assembled quantum dots (original) (raw)
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Single-electron charging and Coulomb interaction in InAs self-assembled quantum dot arrays
Physical Review B
Sequential single-electron charging is observed in InAs Self-Assembled Quantum Dots using capacitance spectroscopy. In this system, the Coulomb energy is smaller than the inter-level energy spacings due to the quantum confinement and both effects can be separately identified. A theoretical model is proposed for this system and the capacitance experiments were devised in order to experimentally observe the effects of Coulomb interaction between electrons on the dots. The effects of inter-and intra-dot Coulomb interaction have been observed in the capacitance spectra. A good agreement between the proposed model and experiment is achieved.
Single electron charging effects in semiconductor quantum dots
Zeitschrift f�r Physik B Condensed Matter, 1991
We have studied charging effects in a lateral split-gate quantum dot defined by metal gates in the two dimensional electron gas (2DEG) of a GaAs/AIGaAs heterostructure. The gate structure allows an independent control of the conductances of the two tunnel barriers separating the quantum dot from the two 2DEG leads, and enables us to vary the number of electrons that are localized in the dot. We have measured Coulomb oscillations in the conductance and the Coulomb staircase in current-voltage characteristics and studied their dependence on the conductances of the tunnel barriers. We show experimentally that at zero magnetic field charging effects start to affect the transport properties when both barrier conductances are smaller than the first quantized conductance value of a point contact at 2 e2/h. The experiments are described by a simple model in terms of electrochemical potentials, which includes both the discreteness of the electron charge and the quantum energy states due to confinement.
Single-electron charging in quantum dots with large dielectric mismatch
Physical Review B, 2001
Semiconductor quantum dots characterized by a strong dielectric mismatch with their environment are studied theoretically through direct diagonalization of the many-body Hamiltonian. The enhancement of the electron-electron Coulomb interaction, arising from polarization effects, is found to induce a strong increase in addition energies with increasing dielectric mismatch. For large dielectric mismatch, the excited many-body states can undergo reconstructions as the dot is filled with carriers even in the absence of external magnetic fields.
Charging of embedded InAs self-assembled quantum dots by space-charge techniques
Physical Review B, 2001
We present the results of both electrical and optical investigations of the charging of InAs self-assembled quantum dots embedded in a space-charge structure. Admittance spectroscopy was employed to study the electronic structures in quantum dots and their electron escape mechanisms. We resolved clear conductance features of different quantum-dot shells, enabling the study of electrons that escaped separately from different shells. Electron-filling modulation reflectance was used to investigate the interband transition influenced by the charging effects. Both the strengths and the energies of the interband transitions were modified in accordance with the electron occupation due to Pauli-blocking and the Coulomb-charging effects. The information acquired from these experimental observations is valuable for feasible device applications.
Coulomb charging effect of electrons in InAs/InAlAs quantum dots studied by capacitance techniques
Physica B: Condensed Matter, 2011
Capacitance-voltage and deep level transient spectroscopy were used to study the capture characteristics of self-assembled InAs/InAlAs quantum dots grown on the InP substrate. It is found that the number of electrons captured by quantum dots can be controlled by varying the width of applied pulse voltage in the DLTS measurements. The Coulomb charging energy and the time of capture can be deduced from the filling time dependent deep level transient spectra.
Surface Science, 2002
The ground-state electronic structure of unsupported three-dimensional cylindrical quantum dots is investigated using a simple free electron model with a step potential. Detailed analysis of the electron structure is presented for different sizes of the quantum dot. The possibility to gain information about the adlayer growth mode from photoemission measurements is discussed and a comparison with experiments is made for the system Na on Cu(1 1 1). We show that an electron structure model study in combination with a STM-dI=dV measurement could give information about the symmetry of the electron states. Such a combined study would make it possible to predict molecular reactivity on quantum dots.
Self-Consistent Analysis of Single Electron Charging Effects in Quantum Dot Nanostructures
2021
We perform a numerical self-consistent simulation of single-electron charging effects in an experimentally fabricated quantum-dot nanostructure. We use an iterative approach based on an extractionorthogonalization method for solving the stationary Schrodinger equation. All relevant quantized regions in the structure are incorporated along with a numerical treatment of the Coulomb blockade and exchange correlation. Transport properties of the structure are evaluated in the adiabatic approximation using an interacting form of the Landauer formula. The theoretically calculated conductance data exhibit good agreement with experiment with respect to peak periodicity but show a strong discrepancy with regard to peak amplitude. This suggests that a high-order effect such as interface disorder may play a large role in determining electronic transmission through tunnel barriers.
Hund's first rule and addition energy spectra of cylindrical quantum dots
Physica E: Low-dimensional Systems and Nanostructures, 2002
We discuss various spin sequences occurring during the charging of realistic vertical quantum dots with emphasis on three-dimensional (3D) e ects. Our analysis is based on a combined theoretical-3D density functional model-experimental approach. In the third shell, a clear dip at N = 7 electrons followed by a peak at N = 8 or 9 is the signature of maximum spin alignment at half-shell ÿlling. ? 2002 Elsevier Science B.V. All rights reserved. PACS: 73.61.−r; 71.15.−m
Applied Physics Letters, 2008
The band structure of self-assembled InAs quantum dots, embedded in a GaAs matrix, is probed with capacitance-voltage spectroscopy and photoluminescence ͑PL͒ spectroscopy. The electron energy levels in the quantum dots with respect to the electron ground state of the wetting layer ͑WL͒ are determined from the capacitance-voltage measurements with a linear lever arm approximation. In the region where the linear lever arm approximation is not valid anymore ͑after the charging of the WL͒, the energetic distance from the electron ground state of the WL to the GaAs conduction band edge can be indirectly inferred from a numerical simulation of the conduction band under different gate voltages. In combination with PL measurements, the complete energy band diagram of the quantum dot sample is extracted.