Detection of efficient carrier capture in ultrathin InAs/GaAs layers using a degenerate pump-probe technique

Liu, Bo; Li, Q; Xu, Zhen‐Jiang; Ge, Weikun

doi:10.1088/0953-8984/13/18/302

Cited by 6 publications

(4 citation statements)

References 21 publications

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“…[ 38 ] Liu et al also reported a similar delayed rise of transient reflectivity in ultrathin InAs/GaAs layers. [ 39 ] The delayed peak was attributed to the carrier capture in ultrathin InAs layers which occurred over a few ps time scale. In another work, Wei‐liang et al had also reported a delayed rise of transient reflectivity signal in GaAs/AlGaAs MQW structure.…”

Section: Resultsmentioning

confidence: 99%

Role of Intra‐Band Relaxation of Holes and Tunneling of Electrons in Carrier Relaxation in AlGaAs/GaAs Quantum Well

Khan

Jayabalan

Khamari

et al. 2022

Physica Status Solidi (b)

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Quantum well (QW) structures are being widely used for many applications like lasers, photodiodes, THz emitters, and many next-generation optoelectronic devices leading to the realization of quantum technology. [1][2][3][4][5][6][7][8][9] Optoelectronic applications of such structures lie in harnessing and controlling the carrier relaxation after carriers are excited or injected into these structures. Many relaxation processes like thermalization, intra-band relaxation, inter-valley scattering, defect-state trapping, and radiative recombination have been reported for such QW structures. [10][11][12][13][14][15] Various time-resolved techniques like pump-probe transmission, transient reflectivity measurements, time-resolved photoluminescence, degenerate four-wave mixing, etc. are used to identify the relaxation mechanism and the corresponding time constants. [11,16,17] Such studies give insight into various dynamical processes that occur at different time scales.Loss of carriers from the QW region can happen due to tunneling of carriers and trapping of carriers by the defect states. Understanding of such carrier loss mechanisms in QW is important for their applications in devices. Several groups have performed various time-resolved measurements to address this issue. [15,[18][19][20] However, some of these processes can compete simultaneously with similar time constants which makes their isolation really difficult and complicates the fundamental understanding of carrier dynamics. Further, most of those measurements were carried out by exciting carriers deep into the conduction band and monitoring the radiative emission from the band edge through the time-resolved PL technique (TRPL). TRPL signal covers only the radiative recombination process and indirectly probes the non-radiative loss. Necessary details about the complete nonradiative processes cannot be addressed by TRPL. In contrast, time-resolved pump-probe reflectivity can give information about both radiative and non-radiative relaxation processes. [21][22][23] In this article, timeresolved pump-probe reflectivity measurements at room temperature are performed on AlGaAs/GaAs QW structure to investigate various ultrafast processes that occur over 0.1-10 ps time scale. Using pump-fluence-dependent studies, the origin of various non-radiative relaxation processes in this QW system is probed. By using numerical calculations, it is shown that the carrier loss from the QW region is mainly governed by the tunneling of electrons. Also, several other ultrafast processes occur on a similar time scale. The various relaxation mechanism occurring within the 10 ps time scale are isolated. After isolation of the processes, the timeresolved nonequilibrium dynamics measurements performed in this work have shown the saturation effect in intraband relaxation due to phonon reabsorption.

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Section: Resultsmentioning

confidence: 99%

Role of Intra‐Band Relaxation of Holes and Tunneling of Electrons in Carrier Relaxation in AlGaAs/GaAs Quantum Well

Khan

Jayabalan

Khamari

et al. 2022

Physica Status Solidi (b)

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“…The probe light monitored only the time evolution of the electron spin in the InGaAs QW. A model based on the rate equations [29] and the Bloch-Torrey equations [5] is proposed to describe the spin transfer processes quantitatively. For the spin-polarized electrons which were generated in the GaAs layer and took part in the spin transfer processes, the time evolution of the spin magnetization can be expressed in the following equations:…”

Section: Resultsmentioning

confidence: 99%

“…With such a system, we studied electron spin transfer processes between two semiconductors of different gaps in an InGaAs/GaAs quantum well (QW) sample. The spin transfer processes are described quantitatively with a model based on the rate equations [29] and Bloch-Torrey equations [5]. We found that the electron spins generated in the GaAs barrier were transferred coherently into the InGaAs QW within 21 ps.…”

Section: Introductionmentioning

confidence: 97%

Direct observation of coherent spin transfer processes in an InGaAs/GaAs quantum well via two-color time-resolved Kerr rotation measurements

Ruan¹,

Sun²,

Yang³

et al. 2008

Semicond. Sci. Technol.

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A two-color time-resolved Kerr rotation spectroscopy system was built, with a femtosecond Ti:sapphire laser and a photonic crystal fiber, to study coherent spin transfer processes in an InGaAs/GaAs quantum well sample. The femtosecond Ti:sapphire laser plays two roles: besides providing a pump beam with a tunable wavelength, it also excites the photonic crystal fiber to generate supercontinuum light ranging from 500 nm to 1600 nm, from which a probe beam with a desirable wavelength is selected with a suitable interference filter. With such a system, we studied spin transfer processes between two semiconductors of different gaps in an InGaAs/GaAs quantum well sample. We found that electron spins generated in the GaAs barrier were transferred coherently into the InGaAs quantum well. A model based on rate equations and Bloch-Torrey equations is used to describe the coherent spin transfer processes quantitatively. With this model, we obtain an effective electron spin accumulation time of 21 ps in the InGaAs quantum well.

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“…After this they can be captured into the wetting layer and then recombine with holes or they can recombine directly from the conduction band. 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).…”

Section: Auger Relaxation Auger Processes and The Dipole Approximationmentioning

confidence: 99%

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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Detection of efficient carrier capture in ultrathin InAs/GaAs layers using a degenerate pump-probe technique

Cited by 6 publications

References 21 publications

Role of Intra‐Band Relaxation of Holes and Tunneling of Electrons in Carrier Relaxation in AlGaAs/GaAs Quantum Well

Role of Intra‐Band Relaxation of Holes and Tunneling of Electrons in Carrier Relaxation in AlGaAs/GaAs Quantum Well

Direct observation of coherent spin transfer processes in an InGaAs/GaAs quantum well via two-color time-resolved Kerr rotation measurements

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

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