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Narvaez, Gustavo A.; Bester, Gabriel; Zunger, Alex

doi:10.1103/physrevb.74.075403

Cited by 77 publications

(29 citation statements)

References 53 publications

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“…A trion may relax energy by a combination of Auger or phonon relaxation for the electron and acoustic phonon emission for the hole, in a time scale of tens of picoseconds. 32,33 Differential transmission measurements mapping the s-shell population as a function of time after the arrival of an excitation pulse resonant with the p-shell estimate the characteristic intershell relaxation time to be 20-30 ps. 26 Let us consider now the generation of spin coherence by the exciting light pulse in more detail.…”

Section: Resultsmentioning

confidence: 99%

Spin coherence generation in negatively charged self-assembled (In,Ga)As quantum dots by pumping excited trion states

et al. 2012

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Spin coherence generation in negatively charged self-assembled (In,Ga)As quantum dots by pumping excited trion states PHYSICAL REVIEW B, COLLEGE PK, v. 86, n. 11, supl Spin coherence generation in an ensemble of negatively charged (In,Ga)As/GaAs quantum dots was investigated by picosecond time-resolved pump-probe spectroscopy measuring ellipticity. Robust coherence of the ground-state electron spins is generated by pumping excited charged exciton (trion) states. The phase of the coherent state, as evidenced by the spin ensemble precession about an external magnetic field, varies relative to spin coherence generation resonant with the ground state. The phase variation depends on the pump photon energy. It is determined by (a) pumping dominantly either singlet or triplet excited states, leading to a phase inversion, and (b) the subsequent carrier relaxation into the ground states. From the dependence of the precession phase and the measured g factors, information about the quantum dot shell splitting and the exchange energy splitting between triplet and singlet states can be extracted in the ensemble.

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Section: Resultsmentioning

confidence: 99%

Spin coherence generation in negatively charged self-assembled (In,Ga)As quantum dots by pumping excited trion states

et al. 2012

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“…17 that the polarization decreases systematically from f-to s-shell. One likely interpretation is that as the electrons relax in energy from higher to lower shells, in each step, there is a finite probability of spin flip of the majority electrons resulting in smaller polarization [43]. Fermi blocking [44] can also contribute to the decrease in polarization.…”

Section: Electrical Control Of Spin Population and Intershell Exchangmentioning

confidence: 97%

“…Each shell collects electrons (holes) from the higher (lower) lying shells as well as the continuum of states in the WL. Intershell electron relaxation times have been calculated by Narvaez et al [43] for empty QDs and found to be short (1-7 ps at low temperatures) compared to recombination times (1 ns) [12].…”

Section: Electrical Control Of Spin Population and Intershell Exchangmentioning

confidence: 97%

Electrical Spin Injection into InGaAs Quantum Dots

Κιοσέογλου¹,

Li²,

Jonker³

2015

Handbook of Spintronics

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The electrical injection of spin-polarized electrons from ferromagnetic Fe contacts into self-assembled InGaAs quantum dots (QDs) incorporated in GaAs/AlGaAs spin light-emitting diode (spin-LED) structures is summarized here. The emissions from the ensemble QDs are efficient and broad in energy due to inhomogeneous broadening (QD size distribution). The circular polarization was measured as functions of current, magnetic field, and temperature. Electrical spin injection at room temperature was achieved, and the spin polarization of the QD emission was found to be remarkably insensitive to temperature. Robust spin polarization was also found in the emission from the InAs wetting layer (WL). At low temperatures, a sharp drop in QD polarization at fields around 5 T is observed, attributed to an efficient magnetic field-induced spin relaxation mechanism involving a two-step process when the dots are occupied by three electron-hole pairs. A modified growth method was also employed to produce low-density and high-uniformity dots to study the spin population of individual shell states. Sequential filling of the s-, p-, d-, and f-shells and the control of their polarization were demonstrated using a spinpolarized current from the Fe contact, and the s-p and p-d intershell exchange energies were determined. These results demonstrate that the spin polarization in InGaAs QDs is robust and can be controlled by a spin-polarized electrical current, an important step toward utilizing QDs in next-generation devices for information processing. List of Abbreviations 2DEG2-dimensional electron gas

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“…The existing pump and probe experiments (Borri et al 2006;Cesari et al 2007;Piwonski et al 2007;Poel et al 2005) show very slow phase recovery and several time constants in the gain and phase recovery, the fastest being subpicosecond. This fast time constant has been generally attributed to Auger mediated carrier capture for InAs ) and InGaAs (Narvaez et al 2006) active layers, through rate-equation excitonic models.…”

Section: Introductionmentioning

confidence: 98%

Modeling of gain and phase dynamics in quantum dot amplifiers

et al. 2008

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By means of an electron hole rate equation model we explain the phase dynamics of a quantum dot semiconductor optical amplifier and the appearance of different decay times observed in pump and probe experiments. The ultrafast hole relaxation leads to a first ultrafast recovery of the gain, followed by electron relaxation and, in the nanosecond timescale, radiative and non-radiative recombinations. The phase dynamics is slower and is affected by thermal redistribution of carriers within the dot. We explain the ultrafast response of quantum dot amplifiers as an effect of hole escape and recombination without the need to assume Auger processes.

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Carrier relaxation mechanisms in self-assembled(In,Ga)As∕GaAsquantum dots: Efficient
Gustavo A. Narvaez
¹
,
Gabriel Bester
²
,
Alex Zunger
³

Cited by 77 publications

References 53 publications

Spin coherence generation in negatively charged self-assembled (In,Ga)As quantum dots by pumping excited trion states

Spin coherence generation in negatively charged self-assembled (In,Ga)As quantum dots by pumping excited trion states

Electrical Spin Injection into InGaAs Quantum Dots

Modeling of gain and phase dynamics in quantum dot amplifiers

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Carrier relaxation mechanisms in self-assembled(In,Ga)As∕GaAsquantum dots: EfficientGustavo A. Narvaez1, Gabriel Bester2, Alex Zunger3

Cited by 77 publications

References 53 publications

Spin coherence generation in negatively charged self-assembled (In,Ga)As quantum dots by pumping excited trion states

Spin coherence generation in negatively charged self-assembled (In,Ga)As quantum dots by pumping excited trion states

Electrical Spin Injection into InGaAs Quantum Dots

Modeling of gain and phase dynamics in quantum dot amplifiers

Contact Info

Product

Resources

About

Carrier relaxation mechanisms in self-assembled(In,Ga)As∕GaAsquantum dots: Efficient
Gustavo A. Narvaez
¹
,
Gabriel Bester
²
,
Alex Zunger
³