Ambipolar drift of spatially separated electrons and holes

Beck, Markus; Streb, D.; Vitzethum, M.; Kiesel, P.; Malzer, S.; Metzner, Claus; Döhler, G. H.

doi:10.1103/physrevb.64.085307

Cited by 17 publications

(10 citation statements)

References 8 publications

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“…The recombination of these excitons gives rise to the large diameter ring pattern. It is important to note that this is a different phenomenon from the related giant ambipolar drift of spatially separated electrons and holes in n-i-p-i superlattice structures 8,9 (see endnote 10 for more explanation).…”

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confidence: 91%

Dynamics of the in-plane charge separation front in a two-dimensional electron-hole gas

Chen¹,

Rapaport²,

Simon³

et al. 2005

Phys. Rev. B

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We show both experimentally and theoretically that the recently observed optically induced inplane charge separation in quantum well (QW) structures and the exciton ring emission pattern at this charge separation boundary have an extremely long lifetime. The oppositely charged carriers remain separated and provide a reservoir of excitons at their boundary with a persistent emission which lasts hundreds of microseconds (orders of magnitude longer than their recombination time)after the external excitation is removed. This long lifetime is due to an interplay between the slow in-plane carrier diffusion and slow carrier tunnelling perpendicular to the QW plane.

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confidence: 91%

Dynamics of the in-plane charge separation front in a two-dimensional electron-hole gas

Chen¹,

Rapaport²,

Simon³

et al. 2005

Phys. Rev. B

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“…[7][8][9][10][11] On the other hand, effects of electron-hole interactions on charge and spin drift in an electric field have not been widely investigated. 12 Here, we image charge and spin drift in p þ GaAs using a polarized microscopy technique described elsewhere. 13 The effect of electron-hole interaction is investigated by generating spin-polarized minority electrons of variable density, using a tightly focused circularly polarized light excitation of variable power (1/e half width of 0:6 lm, energy 1.55 eV).…”

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confidence: 99%

Absence of carrier separation in ambipolar charge and spin drift in p+-GaAs

Cadiz

Paget

Rowe

et al. 2015

Applied Physics Letters

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The electric field-induced modifications of the spatial distribution of photoelectrons, photoholes, and electronic spins in optically pumped p+ GaAs are investigated using a polarized luminescence imaging microscopy. At low pump intensity, application of an electric field reveals the tail of charge and spin density of drifting electrons. These tails disappear when the pump intensity is increased since a slight differential drift of photoelectrons and photoholes causes the buildup of a strong internal electric field. Spatial separation of photoholes and photoelectrons is very weak so that photoholes drift in the same direction as photoelectrons, thus exhibiting a negative effective mobility. In contrast, for a zero electric field, no significant ambipolar diffusive effects are found in the same sample.

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“…As a result, the DP mechanism reduces τ s with increasing E x due to the increased average electron energy. For free electrons and a large electrical bias, a detailed calculation of this effect and its influence on τ s was reported by Beck et al [18].…”

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confidence: 99%

Bias-dependent electron spin lifetimes in n-GaAs and the role of donor impact ionization

Furis

Smith

Reno

et al. 2006

Applied Physics Letters

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In bulk n-GaAs epilayers doped near the metal-insulator transition, we study the evolution of electron spin lifetime τs as a function of applied lateral electrical bias Ex. τs is measured via the Hanle effect using magneto-optical Kerr rotation. At low temperatures (T < 10K, where electrons are partially localized and τs > 100 ns at zero bias), a marked collapse of τs is observed when Ex exceeds the donor impact ionization threshold at ∼10 V/cm. A steep increase in the concentration of warm delocalized electrons -subject to Dyakonov-Perel spin relaxation -accounts for the rapid collapse of τs, and strongly influences electron spin transport in this regime. 72.25.Dc, 72.25.Rb, 79.20.Kz The discovery of very long electron spin lifetimes, τ s , in GaAs has helped motivate considerable interest in semiconductor-based spintronic devices [1]. Studies of bulk n-GaAs have established that, in the absence of any applied electric field, long spin lifetimes in the range τ s =100-300 ns are associated with cryogenic temperatures and electron doping in the range of the metalinsulator transition (n MIT ≃ 2 × 10 16 cm −3 ) [2,3,4,5]. Several prototype devices operating at low temperatures have therefore incorporated n-GaAs doped in this range [6,7,8,9,10,11,12]. This is, however, precisely the doping and temperature regime where carrier transport becomes highly nonlinear due to electron localization (freeze-out) and subsequent impact ionization of donorbound electrons at quite modest applied electric fields of order 10 V/cm [13,14]. Since future spin-transport devices may employ electrical biases on (at least) this order, a bias-dependent study of τ s through the threshold of donor impact ionization is important for device design and for the characterization of spin transport in n-type semiconductors in general.Here we measure τ s as a function of temperature and applied electrical bias E x in bulk epilayers of n-GaAs doped near the metal-insulator transition. τ s is obtained from Hanle depolarization measurements using the magneto-optical Kerr effect. At low temperatures, τ s drops dramatically at the threshold of donor impact ionization at E x ≃ 10 V/cm. At this threshold, which coincides with marked nonlinearities in the samples' currentvoltage (I-V ) characteristics, the electron ensemble becomes largely delocalized (and warm) and the DyakonovPerel spin relaxation mechanism dominates.Three silicon-doped bulk n-GaAs epilayers were grown by molecular beam epitaxy on (001)-oriented GaAs substrates. The dopings and thicknesses are: 1 × 10 16 cm −3 (1 µm thick), 5 × 10 16 cm −3 (1 µm thick), and 4 × 10 15 cm −3 (15 µm thick). These samples allow study of the bias-dependent spin lifetime both above and below the metal-insulator transition (MIT). The inset of Figure 1(a) shows the experimental geometry. The samples are mounted, strain-free, on the cold finger of an optical cryostat. Ohmic contacts of annealed indium or AuGeNi permit application of an in-plane electric field, E x . Spinpolarized electrons are optically inject...

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Ambipolar drift of spatially separated electrons and holes

Cited by 17 publications

References 8 publications

Dynamics of the in-plane charge separation front in a two-dimensional electron-hole gas

Dynamics of the in-plane charge separation front in a two-dimensional electron-hole gas

Absence of carrier separation in ambipolar charge and spin drift in p+-GaAs

Bias-dependent electron spin lifetimes in n-GaAs and the role of donor impact ionization

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