Semiconductor polarization dynamics from the coherent to the incoherent regime: Theory and experiment

Lövenich, R.; Lai, Chih‐Wei; Hägele, D.; Chemla, D. S.; Schäfer, W.

doi:10.1103/physrevb.66.045306

Cited by 15 publications

(14 citation statements)

References 43 publications

(49 reference statements)

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“…The high-quality sample studied here consists of a stack of ten 14-nm wide, undoped GaAs wells separated by 10-nm wide Al 0.3 Ga 0.7 As barriers, grown via molecular beam epitaxy on a GaAs substrate. 30 The structure is embedded in 500 nm-thick Al 0.3 Ga 0.7 As spacer layers. To avoid THz absorption of photoexcited carriers in the substrate, it was removed by selective etching after attaching the QW side to a 0.5-mm thick 100 MgO substrate.…”

Section: Experimental Techniquementioning

confidence: 99%

Transient terahertz spectroscopy of excitons and unbound carriers in quasi-two-dimensional electron-hole gases

et al. 2009

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We report a comprehensive experimental study and detailed model analysis of the terahertz dielectric response and density kinetics of excitons and unbound electron-hole pairs in GaAs quantum wells. A compact expression is given, in absolute units, for the complex-valued terahertz dielectric function of intra-excitonic transitions between the 1s and higher-energy exciton and continuum levels. It closely describes the terahertz spectra of resonantly generated excitons. Exciton ionization and formation are further explored, where the terahertz response exhibits both intra-excitonic and Drude features. Utilizing a two-component dielectric function, we derive the underlying exciton and unbound pair densities. In the ionized state, excellent agreement is found with the Saha thermodynamic equilibrium, which provides experimental verification of the two-component analysis and density scaling. During exciton formation, in turn, the pair kinetics is quantitatively described by a Saha equilibrium that follows the carrier cooling dynamics. The terahertz-derived kinetics is, moreover, consistent with time-resolved luminescence measured for comparison. Our study establishes a basis for tracking pair densities via transient terahertz spectroscopy of photoexcited quasi-two-dimensional electron-hole gases.

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Section: Experimental Techniquementioning

confidence: 99%

Transient terahertz spectroscopy of excitons and unbound carriers in quasi-two-dimensional electron-hole gases

et al. 2009

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“…The second equality in Eq. (23) indicates that P(ω) is, indeed, equivalent to the definition of the spin polarization proposed previously. 14 The generalized spin matrices S are defined in Eq.…”

Section: A Single-particle Spectrummentioning

confidence: 99%

Electron spin orientation under in-plane optical excitation in GaAs quantum wells

et al. 2012

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We study the optical orientation of electron spins in GaAs/AlGaAs quantum wells for excitation in the growth direction and for in-plane excitation. Time-and polarization-resolved photoluminescence excitation measurements show, for resonant excitation of the heavy-hole conduction band transition, a negligible degree of electron spin polarization for in-plane excitation and nearly 100% for excitation in the growth direction. For resonant excitation of the light-hole conduction band transition, the excited electron spin polarization has the same (opposite) direction for in-plane excitation (in the growth direction) as for excitation into the continuum. The experimental results are well explained by an accurate multiband theory of excitonic absorption taking fully into account electron-hole Coulomb correlations and heavy-hole light-hole coupling.

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“…After initial dephasing of coherent polarizations within a few ps [10] incoherent 1s exciton populations remain. Internal exciton transitions occur as shown in Fig.…”

Section: Internal Exciton Transitionsmentioning

confidence: 99%

“…They consist of ten 14-nm wide GaAs quantum wells separated by 10-nm wide Al 0.3 Ga 0.7 As barriers [10]. To avoid effects from the substrate, the layers were attached to MgO and the substrate was removed.…”

Section: Optical-pump Thz-probe Experimentsmentioning

confidence: 99%

Exciton dynamics studied via internal THz transitions

Kaindl

Hägele

Carnahan

et al. 2003

Physica Status Solidi (b)

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We employ a novel, ultrafast terahertz probe to investigate the dynamical interplay of optically-induced excitons and unbound electron-hole pairs in GaAs quantum wells. Resonant creation of heavy-hole excitons induces a new low-energy oscillator linked to transitions between the internal exciton degrees of freedom. The time-resolved terahertz optical conductivity is found to be a probe well suited for studies of fundamental processes such as formation, relaxation and ionization of excitons.

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Semiconductor polarization dynamics from the coherent to the incoherent regime: Theory and experiment

Cited by 15 publications

References 43 publications

Transient terahertz spectroscopy of excitons and unbound carriers in quasi-two-dimensional electron-hole gases

Transient terahertz spectroscopy of excitons and unbound carriers in quasi-two-dimensional electron-hole gases

Electron spin orientation under in-plane optical excitation in GaAs quantum wells

Exciton dynamics studied via internal THz transitions

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