All optical method for investigation of spin and charge transport in semiconductors: Combination of spatially and time-resolved luminescence

Cadiz, Fabian; Barate, Philippe; Paget, D.; Grebenkov, Denis S.; Korb, Jean-Pierre; Rowe, A. C. H.; Amand, T.; Arscott, S.; Peytavit, E.

doi:10.1063/1.4889799

Cited by 20 publications

(29 citation statements)

References 30 publications

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“…However, localized electrons only appear at lattice temperatures smaller than 10K and are absent at the present higher temperature [27]. ii) Since the effective lifetime at r = 0 is ω 2 /4D ≈ 10 ps, the polarization decrease would require an extremely strong, unphysical, decrease of T 1 from its value of 1125 ps at low power [27]. iii) Since an increased spin relaxation at r = 0 does not affect the charge, the present hypothesis cannot explain the observed dependences of the charge diffusion on intensity and polarization reported in Fig.…”

Section: Kinetic Energy Effectsmentioning

confidence: 99%

“…This hypothesis cannot explain the results for three main reasons : i) Such polarization loss can only concern electrons localized in potential fluctuations, since diffusive electrons will transmit their depolarization after diffusion. However, localized electrons only appear at lattice temperatures smaller than 10K and are absent at the present higher temperature [27]. ii) Since the effective lifetime at r = 0 is ω 2 /4D ≈ 10 ps, the polarization decrease would require an extremely strong, unphysical, decrease of T 1 from its value of 1125 ps at low power [27].…”

Section: Kinetic Energy Effectsmentioning

confidence: 99%

“…Finally, time-resolved polarized luminescence measurements as a function of T e were performed in the GaAs sample under consideration [27]. At T e = 50K, one finds τ ef f ≈ 335 ps and T 1 ≈ 1125 ps.…”

Section: Interpretation a Calculation Of The Polarization Profilesmentioning

confidence: 99%

“…(35) and Eq. (36), using an approximate method described in Appendix B and taking for the front and back surface recombination velocities the very weak values in our low temperature conditions S = S = 5 × 10 4 cm/s [27]. The polarization profiles were then calculated using Eq.…”

Section: Interpretation a Calculation Of The Polarization Profilesmentioning

confidence: 99%

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Effect of the Pauli principle on photoelectron spin transport inp+GaAs

et al. 2015

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In p + GaAs thin films, the effect of photoelectron degeneracy on spin transport is investigated theoretically and experimentally by imaging the spin polarization profile as a function of distance from a tightly-focussed light excitation spot. Under degeneracy of the electron gas (high concentration, low temperature), a dip at the center of the polarization profile appears with a polarization maximum at a distance of about 2 µm from the center. This counterintuitive result reveals that photoelectron diffusion depends on spin, as a direct consequence of the Pauli principle. This causes a concentration dependence of the spin stiffness while the spin dependence of the mobility is found to be weak in doped material. The various effects which can modify spin transport in a degenerate electron gas under local laser excitation are considered. A comparison of the data with a numerical solution of the coupled diffusion equations reveals that ambipolar coupling with holes increases the steady-state photo-electron density at the excitation spot and therefore the amplitude of the degeneracy-induced polarization dip. Thermoelectric currrents are predicted to depend on spin under degeneracy (spin Soret currents), but these currents are negligible except at very high excitation power where they play a relatively small role. Coulomb spin drag and bandgap renormalization are negligible due to electrostatic screening by the hole gas.

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Section: Kinetic Energy Effectsmentioning

confidence: 99%

Section: Kinetic Energy Effectsmentioning

confidence: 99%

Section: Interpretation a Calculation Of The Polarization Profilesmentioning

confidence: 99%

Section: Interpretation a Calculation Of The Polarization Profilesmentioning

confidence: 99%

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Effect of the Pauli principle on photoelectron spin transport inp+GaAs

et al. 2015

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“…On the other hand, continuous wave (CW) imaging of spin transport, using luminescence [17], or Kerr microscopy [1] gives diffusion and drift lengths from which it is possible to obtain µτ for the charge transport where µ is the mobility and τ is the lifetime, or µτ s for spin transport where τ s is the spin lifetime. Consequently, CW determination of mobilities or of diffusion constants requires separate determinations of lifetimes [2].In the present work, we investigate spin transport in p-type GaAs using a CW technique in which precession in a magnetic field tranverse to the light excitation acts to effectively time-resolve the experiment so that the relevant parameters for spin drift transport can be determined. As shown in Fig.…”

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confidence: 99%

Luminescence imaging of photoelectron spin precession during drift in a p-type GaAs microfabricated Hall bar

Notot

Paget

Rowe

et al. 2017

Journal of Applied Physics

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Using a microfabricated, p-type GaAs Hall bar, is it shown that the combined application of co-planar electric and magnetic fields enables the observation at 50 K of spatial oscillations of the photoluminescence circular polarization due to the precession of drifting spin-polarized photoelectrons. Observation of these oscillations as a function of electric field E gives a direct measurement of the minority carrier drift mobility and reveals that, for E = 800 V/cm, spin coherence is preserved over a length as large as 25µm. PACS numbers:In the context of future active spintronic devices, the diffusion [1, 2] and drift [3][4][5][6][7][8] of spins in semiconductors have been investigated by numerous authors. N-type GaAs seems particularly promising because of the weak spin relaxation [9], but p-type material cannot be overlooked since in proposed bi-polar spintronic devices [10], it is the minority carrier (electron) spin that determines the common base current gain. While in p-type material charge transport has been investigated [11][12][13], very few studies have considered spin transport [14,15]. Timeresolved investigations have been used [16] but these investigations do not provide a direct spatial imaging. On the other hand, continuous wave (CW) imaging of spin transport, using luminescence [17], or Kerr microscopy [1] gives diffusion and drift lengths from which it is possible to obtain µτ for the charge transport where µ is the mobility and τ is the lifetime, or µτ s for spin transport where τ s is the spin lifetime. Consequently, CW determination of mobilities or of diffusion constants requires separate determinations of lifetimes [2].In the present work, we investigate spin transport in p-type GaAs using a CW technique in which precession in a magnetic field tranverse to the light excitation acts to effectively time-resolve the experiment so that the relevant parameters for spin drift transport can be determined. As shown in Fig. 1, in the same way as performed elsewhere using Kerr microscopy [18,19], we use a microfabricated Hall bar, fabricated from a 3 µm -thick p-type GaAs sample (acceptor doping range 10 18 cm −3 ), with the long axis along which the electric field is applied parallel to the [110] crystallographic direction [20]. The maximum value of of the electric field used here (800 V/cm) is well below that required to saturate the drift velocity at low temperatures [21]. The photoelectrons are generated by a tightly-focussed 12 µW CW excitation by a laser at 1.59 eV, so that transport is not affected by ambipolar effects [14,20], or by Pauli blockade [15,22]. During electron drift in the electric field E, their spin precesses in a magnetic field B (0.23 T) applied in the sample plane. Spin precession results in coherent spatial oscilla- tions of the spin density, which are observed by monitoring the degree of circular polarization of the luminesence in the direction parallel to the photo-excitation wavevector. Qualitatively, the spatial period l of the oscillations is related to the photoelectron...

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Time-Resolved Spin Dynamics and Spin Noise Spectroscopy

Hübner¹,

Oestreich²

2017

Springer Series in Solid-State Sciences

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All optical method for investigation of spin and charge transport in semiconductors: Combination of spatially and time-resolved luminescence

Cited by 20 publications

References 30 publications

Effect of the Pauli principle on photoelectron spin transport inp+GaAs

Effect of the Pauli principle on photoelectron spin transport inp+GaAs

Luminescence imaging of photoelectron spin precession during drift in a p-type GaAs microfabricated Hall bar

Time-Resolved Spin Dynamics and Spin Noise Spectroscopy

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