Auger carrier relaxation in self-assembled quantum dots by collisions with two-dimensional carriers

Uskov, Alexander V.; Adler, F.; Schweizer, H.; Pilkuhn, M. H.

doi:10.1063/1.365363

Cited by 63 publications

(30 citation statements)

References 15 publications

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“…Since in each scattering event the total energy must be conserved, the scattering of one carrier to a lower state must be accompanied by the scattering of the scattering partner to a higher energy with equal energy difference. This type of process is known as Augerscattering [SCH87,USK97a]. Since the total energy of the charge carriers is conserved, Auger-scattering will lead to a change of charge-carrier temperature.…”

Section: Charge-carrier Scattering In Quantum-dot Structuresmentioning

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: Charge-carrier Scattering In Quantum-dot Structuresmentioning

confidence: 99%

Nonlinear and Nonequilibrium Dynamics of Quantum-Dot Optoelectronic Devices

Lingnau

2015

Springer Theses

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“…The processes involved, carrier capture into the dots and intradot relaxation, have been under extensive research during the past decade, both experimentally and theoretically. 4 -15 Two different capture and relaxation processes have been considered; via carrier-carrier interaction ͑Auger processes͒ 5,6,13,14 or via carrier-phonon coupling. 6,7,[10][11][12] In Ref.…”

Section: Introductionmentioning

confidence: 99%

One- and two-phonon capture processes in quantum dots

Magnúsdóttir

Uskov

Bischoff

et al. 2002

Journal of Applied Physics

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“…Until now, most work on Auger relaxation has involved model dot states with rates calculated in the dipole approximation (Uskov, 1997). At first sight the dipole approximation should be very accurate because of the small spatial extent of the dot states but we have found a surprising discrepancy between exact Auger rates and rates calculated in the dipole approximation.…”

Section: Introductionmentioning

confidence: 72%

“…This process is described by the following rate equations (10) where the time constants are taken from experimental data of Liu et al (Liu, 2001) ( ps, ps, ns, ns) and the injection rate is chosen to give the desired number of injected electrons. Auger relaxation rate calculations for electrons in a self-assembled dot were first performed by Uskov et al (Uskov, 1997). They used an axially symmetric dot model so the dot states contain an angular momentum factor, identical to the factor that appears in the basis states defined in Eq.…”

Section: Auger Relaxation Auger Processes and The Dipole Approximationmentioning

confidence: 99%

“…We suppose that the dot electron interacts with the external electron via the screened Coulomb interaction, (9) where r and r are the dot and external electron coordinates, is the dielectric constant, is the Debye screening constant, and and are the bulk electron density and temperature. The screening effect of the wetting layer electrons is neglected (Uskov, 1997).…”

Section: Auger Relaxation Auger Processes and The Dipole Approximationmentioning

confidence: 99%

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Efficient Calculation of Electron States in Self-Assembled Quantum Dots: Application to Auger Relaxation

Chaney

Roy

Maksym

Quantum Dots: Fundamentals, Applications, and Frontiers

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An efficient method for calculation of self-assembled dot states within the effective mass approximation is described and its application to the calculation of Auger relaxation rates is detailed. The method is based on expansion of the dot states in a harmonic oscillator basis whose parameters are optimised to improve the convergence rate. This results in at least an order of magnitude reduction in the number of basis states required to represent electron states accurately compared to the conventional plane wave approach. Auger relaxation rates are calculated for harmonic oscillator model states and exact states for various pyramidal models. The dipole approximation, previously used to calculate Auger rates, is found to be inaccurate by a factor of around 2-3. The harmonic oscillator states do not reproduce the rates for the more realistic pyramidal models very well and even within the set of pyramidal models variations in the dot shape and size can change the rates by up to an order of magnitude. Typical Auger relaxation rates are on a picosecond timescale but the actual value is strongly dependent on the density of electrons outside the dot.

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Auger carrier relaxation in self-assembled quantum dots by collisions with two-dimensional carriers

Cited by 63 publications

References 15 publications

Nonlinear and Nonequilibrium Dynamics of Quantum-Dot Optoelectronic Devices

Nonlinear and Nonequilibrium Dynamics of Quantum-Dot Optoelectronic Devices

One- and two-phonon capture processes in quantum dots

Efficient Calculation of Electron States in Self-Assembled Quantum Dots: Application to Auger Relaxation

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