Quantum-confined Stark effect and built-in dipole moment in self-assembled InAs∕GaAs quantum dots

Jin, Peng; Li, C. M.; Zhang, Z. Y.; Liu, F. Q.; Chen, Y. H.; Ye, X. L.; Xu, Bin; Wang, Z. G.

doi:10.1063/1.1801678

Cited by 41 publications

(29 citation statements)

References 17 publications

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“…At the maximum current of j = 1000 mA that we will use here, the square of the dipole moment, and thus the gain, is reduced to 71% of its original value. This phenomenological change of the resulting gain is used to explain effects that are not intrinsically included in the quantum-dot amplifier model, e.g., the quantum-confined stark effect at higher bias voltages that leads to a decrease of the dipole moment [SCH99,JIN04]. Furthermore, the dephasing time T 2 of the quantum-dot transitions is known to depend on charge-carrier density and temperature [BOR02,NIL05,LOR06,KOP11,GOL14].…”

Section: Calculation Of Amplified Spontaneous Emission Spectramentioning

confidence: 99%

Nonlinear and Nonequilibrium Dynamics of Quantum-Dot Optoelectronic Devices

Lingnau

2015

Springer Theses

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In this thesis the dynamics and performance of optoelectronic devices based on semiconductor quantum-dots are investigated.In the first part, the dynamics of quantum-dot lasers under external perturbations is discussed. Using a microscopically based balance equation model that incorporates detailed charge-carrier scattering dynamics and the possibility to describe nonequilibrium between intra-band electronic states, the relaxation oscillations of the quantum-dot laser are investigated. Three qualitatively different dynamic regimes are identified in dependence of the scattering rates -the "constantreservoir" regime for slow scattering, the "overdamped" regime, and the "synchronized" regime for high scattering -characterized by a varying degree of nonequilibrium between the quantum-dot and reservoir states.Important differences to conventional lasers are found in the modulation response and the dynamics in optical injection and feedback setups. Common theoretical models and approaches used to describe these applications are shown to yield inaccurate predictions, especially in the "constant-reservoir" and "overdamped" dynamic regimes. An important consequence is that the amplitude-phase coupling in quantum-dot lasers, commonly described by the α-factor, differs from conventional descriptions due to the desynchronization of gain and refractive index. While the α-factor describes bifurcations of fixed points accurately, it fails in describing dynamic solutions and overestimates the extent of complex dynamics. The observed low sensitivity to optical perturbations in quantum-dot lasers can therefore be attributed partly to the charge-carrier nonequilibrium. Three quantum-dot laser models on different levels of sophistication are presented that can accurately describe the quantum-dot nonequilibrium dynamics.In the second part of the thesis, the performance of quantum-dot semiconductor optical amplifiers is investigated, and two types of applications unique to quantum-dots as active medium are discussed. The ground and excited states of the quantum-dots allow an ultra-broad-band amplification of optical data streams. Amplified signals on the ground-state frequencies are shown to generally exhibit higher quality than on the excited state, due to a lower sensitivity of the groundstate to carrier-density variations. Nevertheless the quantum-dot amplifier is found to allow effective amplification on both frequency ranges. Furthermore, a parameter range is identified that allows for a simultaneous amplification of data signals on the ground and excited state in a counter-propagating setup.The long microscopically polarization dephasing times in quantum-dots are found to enable quantum-coherent interactions on a macroscopic scale at room-temperature. By comparison with experiments, the occurrence of Rabi-oscillations by amplification of ultra-short pulses is demonstrated. Quantum-dot based devices could therefore be used for future applications based on quantum-coherent effects.

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Section: Calculation Of Amplified Spontaneous Emission Spectramentioning

confidence: 99%

Nonlinear and Nonequilibrium Dynamics of Quantum-Dot Optoelectronic Devices

Lingnau

2015

Springer Theses

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“…Recently QCSE in semiconductor quantum-dot (QD) has been extensively investigated both theoretically and experimentally. [2][3][4][5] The three-dimensional (3D) confinement in QD leads to enhanced nonlinearities and electro-optic properties, which would result in electro-optic modulation devices with even greater efficiency. [6] In addition, the fine manipulating of the QD electronic states utilizing the Stark effect are essential for quantum information applications.…”

Section: Introductionmentioning

confidence: 99%

Quantum-confined Stark effects in interdiffused semiconductor quantum dots

et al. 2007

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Quantum-confined Stark effect in zero-dimensional semiconductor quantum-dot (QD) has attracted considerable interest due to the potential applications in electro-optic modulation and quantum computing. Composition interdiffusion occurs easily during the high temperature epitaxial growth or ex situ annealing treatment, therefore understanding the effects of interdiffusion is essential for device design and modeling. However, relatively little attention has been devoted to a systematic study of this effect. In this paper, the effects of isotropic interdiffusion on the optical transition energy of self-assembled InAs/GaAs QD structure under an electric field have been investigated theoretically. Our three-dimensional QD calculation is based on coupled QDs with different shapes arranged periodically in a tetragonal superlattice, taking into account the finite band offset, valence-band mixing, strain, and effective mass anisotropicity. The electron and hole Hamiltonians with the interdiffusion effect are solved in the momentum space domain. Our results show that isotropic three-dimensional In-Ga interdiffusion will makes the Stark shift become more symmetry about 0 = F in asymmetric lens-shaped and pyramidal QDs, implying the reduced build-in dipole momentum. The interdiffusion also leads to enhanced Stark shift with more prominent effects to QDs that are under larger electric fields.

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“…The dependence of the transition energy e T on the applied electric field is defined by a quadratic relation in the literature [11][12][13][14][15][16], e T (E) = e T (0) + ρE + βE 2 (5) where e T (0) and e T (E) are the ground state transition energies with the applied electric field values of zero and E, respectively. ρ depends on the built in dipole moment and β is a measure of the polarizibility of the electron and hole wave functions.…”

Section: -Quantum Confined Stark Effectmentioning

confidence: 99%

“…While the asymmetric quantum confined stark effect (QCSE) and the presence of a permanent dipole moment due to a vertically applied electric field are well known and have been studied in detail in the past [11][12][13][14], very little is known about the dependence of the ground state transition energy, the optical transition rate and the carrier wave function response to an applied in-plane electric field. In contrast to the vertical field results, experiments [15,16] have demonstrated the absence of an in-plane dipole moment in the lateral direction.…”

Section: -Introductionmentioning

confidence: 99%