Transmission-grating-photomasked transient spin grating and its application to measurement of electron-spin ambipolar diffusion in (110) GaAs quantum wells

Chen, Ke; Wang, Wenfang; Wu, Jingda; Schuh, Dieter; Wegscheider, Werner; Korn, Tobias; Lai, Tianshu

doi:10.1364/oe.20.008192

Cited by 10 publications

(15 citation statements)

References 19 publications

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“…(By contrast, Eq. 6 shows that for n-type samples D a never decreases with n, consistent with measurements in nominally undoped 11,12 and Si-doped 15 GaAs quantum wells.) Figure 3(b) shows D a /µ h calculated for a sample doped as heavily as ours.…”

Section: Numerical Evaluation Of Eqsupporting

confidence: 77%

Diffusion of degenerate minority carriers in a p-type semiconductor

Weber

Kittlaus

2013

Journal of Applied Physics

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We report ultrafast transient-grating experiments on heavily p-type InP at 15 K. Our measurement reveals the dynamics and diffusion of photoexcited electrons and holes as a function of their density n in the range 2 × 10 16 to 6 × 10 17 cm −3 . After the first few picoseconds the grating decays primarily due to ambipolar diffusion. While at low density we observe a regime in which the ambipolar diffusion is electron-dominated and increases rapidly with n, at high n it appears to saturate at 34 cm 2 /s. We present a simple calculation that reproduces the main results of our measurements as well as of previously published measurements that had shown diffusion to be a flat or decreasing function of n. By accounting for effect of density on charge susceptibility we show that, in p-type semiconductors, the regime we observe of increasing ambipolar diffusion is unique to heavy doping and low temperature, where both the holes and electrons are degenerate; in this regime the electronic and ambipolar diffusion are nearly equal. The saturation is identified as a crossover to ambipolar diffusion dominated by the majority carriers, the holes. At short times the transient-grating signal rises gradually. This rise reveals cooling of hot electrons and, at high photocarrier density, allows us to measure ambipolar diffusion of 110 cm 2 /s in the hot-carrier regime.

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Section: Numerical Evaluation Of Eqsupporting

confidence: 77%

Diffusion of degenerate minority carriers in a p-type semiconductor

Weber

Kittlaus

2013

Journal of Applied Physics

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“…Spin relaxation dynamics of electrons has been studied extensively in bulk GaAs semiconductors 1–7 and two-dimensional GaAs quantum wells 7–15 . It was found that spin relaxation time of electrons was dominated by the Dyakonov-Perel (DP) spin relaxation mechanism for both (001)-oriented bulk GaAs 1, 3, 7 and two-dimensional quantum wells 10 , but the DP spin relaxation mechanism was suppressed so substantially in (110)-oriented GaAs quantum wells that spin relaxation time was prolonged significantly 14, 15 . In contrast to the extensive studies of spin relaxation of electrons, spin relaxation of holes in bulk GaAs and quantum wells was studied much less because spin relaxation of holes was much faster than one of electrons and usually hidden by spin relaxation of electrons.…”

Section: Introductionmentioning

confidence: 99%

Spin relaxation dynamics of holes in intrinsic GaAs quantum wells studied by transient circular dichromatic absorption spectroscopy at room temperature

Fang

Zhu

Lai

2017

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Spin relaxation dynamics of holes in intrinsic GaAs quantum wells is studied using time-resolved circular dichromatic absorption spectroscopy at room temperature. It is found that ultrafast dynamics is dominated by the cooperative contributions of band filling and many-body effects. The relative contribution of the two effects is opposite in strength for electrons and holes. As a result, transient circular dichromatic differential transmission (TCD-DT) with co- and cross-circularly polarized pump and probe presents different strength at several picosecond delay time. Ultrafast spin relaxation dynamics of excited holes is sensitively reflected in TCD-DT with cross-circularly polarized pump and probe. A model, including coherent artifact, thermalization of nonthermal carriers and the cooperative contribution of band filling and many-body effects, is developed, and used to fit TCD-DT with cross-circularly polarized pump and probe. Spin relaxation time of holes is achieved as a function of excited hole density for the first time at room temperature, and increases with hole density, which disagrees with a theoretical prediction based on EY spin relaxation mechanism, implying that EY mechanism may be not dominant hole spin relaxation mechanism at room temperature, but DP mechanism is dominant possibly.

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“…The mobility in these systems, however, is very low due to the direct doping, and they do not allow for easy manipulation of the carrier density and the Rashba spin-orbit interaction by external gate voltages. Optical measurements of spin diffusion in QWs and 2DES are in many cases more challenging, as the spin diffusion length is shorter due to fast dephasing, so that techniques such as transient spin gratings [28] or shadow gratings [29] need to be applied. Large spin diffusion lengths can be observed in (110)-grown QWs in which carrier transport is facilitated by surface acoustic waves [30][31][32] and in (110)-oriented 2DES [21,33].…”

Section: Introductionmentioning

confidence: 99%

Spin polarization, dephasing, and photoinduced spin diffusion in (110)-grown two-dimensional electron systems

et al. 2014

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We study the optically induced spin polarization, spin dephasing, and diffusion in several high-mobility twodimensional electron systems, which are embedded in GaAs quantum wells grown on (110)-oriented substrates. The experimental techniques comprise a two-beam magneto-optical spectroscopy system and polarizationresolved photoluminescence. Under weak excitation conditions at liquid-helium temperatures, we observe spin lifetimes above 100 ns in one of our samples, which are reduced with increasing excitation density due to additional, hole-mediated, spin dephasing. The spin dynamic is strongly influenced by the carrier density and the ionization of remote donors, which can be controlled by temperature and above-barrier illumination. The absolute value of the average electron spin polarization in the samples is directly observable in the circular polarization of photoluminescence collected under circularly polarized excitation and reaches values of about 5%. Spin diffusion is studied by varying the distance between pump and probe beams in microspectroscopy experiments. We observe diffusion lengths above 100 μm and, at high excitation intensity, a nonmonotonic dependence of the spin polarization on the pump-probe distance.

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Transmission-grating-photomasked transient spin grating and its application to measurement of electron-spin ambipolar diffusion in (110) GaAs quantum wells

Cited by 10 publications

References 19 publications

Diffusion of degenerate minority carriers in a p-type semiconductor

Diffusion of degenerate minority carriers in a p-type semiconductor

Spin relaxation dynamics of holes in intrinsic GaAs quantum wells studied by transient circular dichromatic absorption spectroscopy at room temperature

Spin polarization, dephasing, and photoinduced spin diffusion in (110)-grown two-dimensional electron systems

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