Spin Accumulation and Spin Lifetime in p-Type Germanium at Room Temperature

Iba, Satoshi; Saito, H.; Spiesser, A.; Watanabe, S.; Jansen, R.; Yuasa, Shinji; Ando, Koji

doi:10.1143/apex.5.053004

Cited by 38 publications

(71 citation statements)

References 28 publications

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“…The spin RA product also displays an exponential variation with thickness of the tunnel oxide, and a power law is revealed when the spin RA product is plotted against tunnel resistance [see Figs [20,21], we also find that R tun and the spin RA product vary exponentially with MgO thickness [see Fig. 3(c)], although the data set is too limited to extract an accurate value for the scaling exponent.…”

Section: Scaling With Tunnel Barrier Thicknessmentioning

confidence: 74%

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Anomalous scaling of spin accumulation in ferromagnetic tunnel devices with silicon and germanium

et al. 2014

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Anomalous scaling of spin accumulation in ferromagnetic tunnel devices with silicon and germanium Sharma, S.; Spiesser, A.; Dash, S.P.; Iba, S.; Watanabe, S.; Wees, B.J. van; Saito, H.; Yuasa, S.; Jansen, R. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. The magnitude of spin accumulation created in semiconductors by electrical injection of spin-polarized electrons from a ferromagnetic tunnel contact is investigated, focusing on how the spin signal detected in a Hanle measurement varies with the thickness of the tunnel oxide. An extensive set of spin-transport data for Si and Ge magnetic tunnel devices reveals a scaling with the tunnel resistance that violates the core feature of available theories, namely, the linear proportionality of the spin voltage to the injected spin current density. Instead, an anomalous scaling of the spin signal with the tunnel resistance is observed, following a power law with an exponent between 0.75 and 1 over 6 decades. The scaling extends to tunnel resistance values larger than 10 9 μm 2 , far beyond the regime where the classical impedance mismatch or back flow into the ferromagnet play a role. This scaling is incompatible with existing theory for direct tunnel injection of spins into the semiconductor. It also demonstrates conclusively that the large spin signal does not originate from two-step tunneling via localized states near the oxide/semiconductor interface. Control experiments show that spin accumulation in localized states within the tunnel barrier or artifacts are also not responsible. Altogether, the scaling results suggest that, contrary to all existing descriptions, the spin signal is proportional to the applied bias voltage, rather than the (spin) current.

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Section: Scaling With Tunnel Barrier Thicknessmentioning

confidence: 74%

“…Tunnel devices on p-type Ge(001) were prepared using Ga-doped wafers with a resistivity of 3 m cm and a carrier concentration of 8.2 × 10 18 cm −3 at 300 K. The preparation of the epitaxial MgO/Fe tunnel contacts on Ge was as previously described [21].…”

Section: Device Fabricationmentioning

confidence: 99%

Anomalous scaling of spin accumulation in ferromagnetic tunnel devices with silicon and germanium

et al. 2014

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“…[23][24][25] as well as into Ge through MgO. [26][27][28][29][30][31][32][33][34] Among the latest experiments, the transformation of a spin-polarized electron current into left-or righthanded circularly polarized light in a spin light-emitting diode (spin LED) integrating a III-V semiconductor heterostructure 8,11,[13][14][15][16][17]19,23,34,35 is one of the most striking physical phenomena. The electric dipolar selection rules involved in a quantum well 36 (QW) embedded in a spin LED during electron-hole recombination require spin injection with an out-of-plane magnetization.…”

Section: Introductionmentioning

confidence: 99%

Spin injection at remanence into III-V spin light-emitting diodes using (Co/Pt) ferromagnetic injectors

et al. 2012

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We have studied the perpendicular magnetic anisotropy of Co/Pt multilayers and the electron spin injection efficiency by optical spectroscopy from a [Co(0.6 nm)/Pt(1 nm)] 4 /Fe(0.3 nm)/MgO perpendicular tunnel spin injector grown on AlGaAs/GaAs semiconductor light-emitting diodes. We observe a 2.5% circular polarization at low temperature close to the magnetic remanence when the 0.3 nm Fe film of the ferromagnetic injector is sufficiently thin to maintain the magnetization out of plane. The acquired squared magnetization cycle is explained by the remaining interlayer exchange coupling existing between Fe and the (Co/Pt) multilayer through Pt or possible perpendicular magnetic anisotropy at the MgO/Fe interface. The corresponding spin polarization of the current is then estimated as 7%, measured by photoluminescence techniques, after the necessary uprenormalization, taking into account the electron spin-flip rate in the quantum well. In contrast, no circular polarization is observed when the thin Fe layer is removed and despite the rather high magnetic polarizability of the 5d 9 electronic open shell of Pt at the interface with MgO. This emphasizes the reduced size of tunneling branching of wave functions at the interface, of the order of the atomic plane unit.

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“…Spin related properties such as spin injection efficiency from a ferromagnetic metal (FM) into a SC and spin lifetime in the SC were also discussed by analyzing the spin accumulation signals [1][2][3][4][5][6][7][8][9][10][11]. However, reliability of the estimated values of the spin related properties is now open for discussion.…”

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confidence: 99%

“…Hereafter, we focus on the effect of the magnetic domain structure in the FM contact used on the spin accumulation signals as one of the possible origins of the discrepancies between theories and experiments, because variously-sized FM contacts which can give rise to various magnetic domain structures have so far been utilized for the 3T measurements in the previous studies [1][2][3][4][5][6][7][8][9][10][11]. For the spin valve devices with multiple FM contacts which can detect the spin accumulation after intermixing of whole injected spins, it has been revealed that the magnetic domain structure of the spin injector strongly affects the spin accumulation signals [13].…”

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confidence: 99%

Effect of the magnetic domain structure in the ferromagnetic contact on spin accumulation in silicon

Ando

Yamada

Kasahara

et al. 2012

Applied Physics Letters

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Spin Accumulation and Spin Lifetime in p-Type Germanium at Room Temperature

Cited by 38 publications

References 28 publications

Anomalous scaling of spin accumulation in ferromagnetic tunnel devices with silicon and germanium

Anomalous scaling of spin accumulation in ferromagnetic tunnel devices with silicon and germanium

Spin injection at remanence into III-V spin light-emitting diodes using (Co/Pt) ferromagnetic injectors

Effect of the magnetic domain structure in the ferromagnetic contact on spin accumulation in silicon

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