Time-resolved Raman scattering in GaAs quantum wells

Oberli, D. Y.; Wake, D. R.; Klein, Michael W.; Klem, John F.; Henderson, T.; Morkoç̌, H.

doi:10.1103/physrevlett.59.696

Cited by 220 publications

(42 citation statements)

References 21 publications

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“…It was therefore thought that there is a considerable advantage in working in this frequency range since LO phonon emission-which represents the competing non-radiative loss mechanism-should be eliminated. However, recent experimental work on wide quantum wells has yielded a range of intersubband lifetimes, from 200 ps ͑characteristic of the acoustic phonon scattering regime͒ 2 to approximately 1 ps ͑implying incomplete suppression of LO phonon scattering͒. 3 Determination of intersubband lifetimes is therefore an important aspect in the successful design of both a terahertz emitter and a laser.…”

Section: Introductionmentioning

confidence: 99%

Population inversion in optically pumped asymmetric quantum well terahertz lasers

Harrison

Kelsall

1997

Journal of Applied Physics

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Intersubband carrier lifetimes and population ratios are calculated for three-and four-level optically pumped terahertz laser structures. Laser operation is based on intersubband transitions between the conduction band states of asymmetric GaAs-Ga 1Ϫx Al x As quantum wells. It is shown that the carrier lifetimes in three-level systems fulfill the necessary conditions for stimulated emission only at temperatures below 200 K. The addition of a fourth level, however, enables fast depopulation of the lower laser level by resonant longitudinal optical phonon emission and thus offers potential for room temperature laser operation.

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Section: Introductionmentioning

confidence: 99%

Population inversion in optically pumped asymmetric quantum well terahertz lasers

Harrison

Kelsall

1997

Journal of Applied Physics

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“…As the well width decreases the effect of the MQW potential on the zone-folded acoustic phonon modes enhances and leads to an increase of the acoustic-phonon contribution to the intra-impurity scattering rate. For intersubband scattering of electrons in the GaAs MQWs, the acoustic-phonon contribution to the intersubband scattering rate is inversely proportional to the square of the well width [10]. A similar dependence of the overlap between the localized impurity states and the acoustic phonon modes could also explain the monotonically decreasing 2p excited state lifetime with well width.…”

Section: Resultsmentioning

confidence: 95%

Picosecond time‐resolved studies of excited state lifetime of Be acceptor in GaAs/AlAs multiple quantum wells

Zheng

Halsall

Harrison

et al. 2002

Physica Status Solidi (b)

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The influence of the quantum well potential on the carrier dynamics of holes bound to the acceptors in Be δ-doped AlAs/GaAs multiple quantum wells is investigated by far-infrared time-resolved spectroscopy using the Free-Electron Laser for Infrared eXperiments (FELIX). The lifetime of the 2p excited state of acceptors was measured as a function of the width of the quantum well and the temperature. It is found that the lifetime decreases monotonically with decreasing well width and is independent of temperature. We suggest that the relaxation process of the 2p → 1s is non-radiative and mediated via confined acoustic phonon modes, in particular, zone-folded acoustic phonon modes which arise from the periodic nature of the multiple quantum well samples. For one particular well width the lifetime was measured across the inhomogeneously broadened D-line as 30, 30, 70, and 105 ps for 43, 44, 46, and 47 µm wavelengths, respectively. We believe the latter is due to diffusion of the Be δ-doped atomic layer in the quantum wells.Introduction In multiple quantum well or superlattice structures, the artificial period along the direction perpendicular to the layers results in Brillouin-zone folding and produces additional phonon branches and gaps in the phonon spectrum [1 -3]. Zone-folded acoustic phonons are in general accessible by the interaction with photons or carriers and have been reported in Raman scattering studies of GaAs/AlAs superlattices [1,4]. Zucker et al. has discovered a new deformation-potential electronphonon scattering in GaAs quantum wells, which does not exist in bulk GaAs [5] and is thought to arise from the change in symmetry of the crystal lattice. Such changes in symmetry can produce more efficient phonon scattering at energies which are larger than the typical bulk acoustic phonon energy of a few meV, but less than the dominant longitudinal optic (LO) phonon mode. In this paper we investigate hole scattering which is in just this regime -the influence of the quantum well potential on the carrier dynamics of holes bound to Be acceptors in δ-doped AlAs/GaAs MQW.

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“…This is a consequence of the quenching of the LO-phonon emission when the ISB transition energy is below the LO-phonon energy, which is well documented, for example, in GaAs/ AlGaAs QWs. [23][24][25][26][27] This huge increase of the ISB relaxation time opens great prospects for efficient nitride ISB devices at long wavelengths.…”

Section: ͑9͒mentioning

confidence: 99%

“…Typical ISB relaxation times in GaAs quantum wells range from ϳ0.3-2 ps for mid-infrared transitions ͑LO-phonon emission͒ to ϳ100-400 ps for far-infrared transitions ͑acoustic phonon emission͒. [23][24][25][26][27] GaN, with a LOphonon energy E LO = 92 meV compared with 36 meV for GaAs, opens interesting opportunities in this context. Nowadays the maturity of the plasma-assisted molecular-beam epitaxy ͑PAMBE͒ of GaN / AlGaN heterostructures renders feasible the realization of band-engineered structures required to observe and exploit these ISB effects.…”

Section: Introductionmentioning

confidence: 98%

Observation of hot luminescence and slow inter-sub-band relaxation in Si-doped GaN∕AlxGa1−xN (x=0.11, 0.25) multi-quantum-well structures

Monroy

Guillot

Gayral

et al. 2006

Journal of Applied Physics

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We report on the growth, structural, electronic, and optical properties of Si-doped GaN∕AlxGa1−xN (x=0.11, 0.25) multiple-quantum-well structures grown on SiC by plasma-assisted molecular-beam epitaxy. We have demonstrated that the use of In as a surfactant during growth improves the structural and optical properties of these layers. Photoluminescence studies have made possible the identification of the fundamental and excited electronic levels by comparison with simulations of the electronic structure. Temperature dependence studies reveal an anomalous behavior of the photoluminescence intensity, which is the quenching of the e1−hh1 line, while the e2−hh1 and e3−hh1 transitions become dominant at room temperature in the samples with 11% and 25% Al in the barrier, respectively. This behavior can be explained by the population of the e2 and e3 electronic states by thermally excited carriers, and by the higher oscillator strength of e2−hh1 and e3−hh1 transitions compared with e1−hh1, due to the intense electric field in the quantum wells. Long inter-sub-band (ISB) relaxation times (40–100ps) have been measured in GaN∕AlGaN multiple quantum wells, as a consequence of the quenching of the longitudinal optical (LO)-phonon emission when the ISB transition energy is below the LO-phonon energy.

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Time-resolved Raman scattering in GaAs quantum wells

Cited by 220 publications

References 21 publications

Population inversion in optically pumped asymmetric quantum well terahertz lasers

Population inversion in optically pumped asymmetric quantum well terahertz lasers

Picosecond time‐resolved studies of excited state lifetime of Be acceptor in GaAs/AlAs multiple quantum wells

Observation of hot luminescence and slow inter-sub-band relaxation in Si-doped GaN∕AlxGa1−xN (x=0.11, 0.25) multi-quantum-well structures

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