Spin Transport and Relaxation up to 250 K in Heavily Doped 
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Fujita, Y.; Yamada, Michihiro; Tsukahara, Makoto; Oka, Tetsuo; Yamada, Shinya; Kanashima, Takeshi; Sawano, Kentarou; Hamaya, Kohei

doi:10.1103/physrevapplied.8.014007

Cited by 55 publications

(78 citation statements)

References 75 publications

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“…For both LSVs, all the parameters are nearly the same, meaning that the post annealing at 300 • C did not affect τ Ge , D, and λ Ge . In addition these values are consistent with the experimental data previously reported 19,24,25 and the expected values from the recent theoretical studies for heavily doped n-Ge 34,35 . For these reasons, we deduce that the magnitude of the nonlocal spin transport signals is significantly influenced by factors different than the spin lifetime and the spin diffusion length in the spin transport layers.…”

supporting

confidence: 92%

“…Furthermore, it is of crucial importance knowing how annealing, a common procedure in Heusler based spin-devices undertaken for improving the structural and chemical ordering of the deposited films, will affect spin polarization and overall magnetic/electronic properties of Heusler/SC based devices. Recently, for n-type Ge, we have pioneered and demonstrated the spin injection/detection techniques with ferromagnetic Heusleralloy/Ge heterointerfaces 20,24,25 , which allow us to address the relevant interface phenomena using the LSVs with the Heusler-alloy/Ge contacts.…”

mentioning

confidence: 99%

“…1(a). Here we used Co 2 FeAl 0.5 Si 0.5 (CFAS) as a spin injector and a detector 24,25 . To promote the tunneling conduction for spin injection and detection, a P δ-doped Ge layer with an ultra-thin Si insertion was grown at CFAS/n-Ge interfaces.…”

mentioning

confidence: 99%

“…To promote the tunneling conduction for spin injection and detection, a P δ-doped Ge layer with an ultra-thin Si insertion was grown at CFAS/n-Ge interfaces. The detailed procedures of the crystal growth of CFAS films and n-Ge spin-transport layers were shown elsewhere 24,26,27 . The carrier concentration (n) in the n-Ge layer was n ∼ 8.0 × 10 18 cm −3 , estimated from the Hall-effect measurements.…”

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confidence: 99%

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Correlation between spin transport signal and Heusler/semiconductor interface quality in lateral spin-valve devices

et al. 2018

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We show a direct evidence for the impact of Heusler/semiconductor interfaces atomic structure on the spin transport signals in semiconductor-based lateral spin-valve (LSV) devices. Based on atomic scale Z contrast scanning transmission electron microscopy and energy dispersive x-ray spectroscopy we show that atomic order/disorder of Co2FeAl0.5Si0.5 (CFAS)/n-Ge LSV devices is critical for the spin injection in Ge. By conducting a post annealing of the LSV devices, we find 90% decrease in the spin signal while there is no difference in the electrical properties of the CFAS/n-Ge contacts and in the spin diffusion length of the n-Ge layer. We show that the reduction in the spin signals after annealing is attributed to the presence of intermixing phases at the Heusler/semiconductor interface. First principles calculations show how that intermixed interface region has drastically reduced spin polarisation at the Fermi level, which is the main cause for the significant decrease of the spin signal in the annealed devices above 300 • C.

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confidence: 92%

mentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Correlation between spin transport signal and Heusler/semiconductor interface quality in lateral spin-valve devices

et al. 2018

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“…In this article, to simultaneously achieve highly efficient spin injection at room temperature and low contact resistance in SC devices, we present an efficient spin injection technique using an FM-FM-SC heterostructure, where the top FM electrode is a ferromagnetic Heusler alloy, Co 2 FeAl 0.5 Si 0.5 (CFAS), the middle FM is atomically controlled iron (Fe) layers, and the SC is germanium (Ge), which not only is a next-generation channel material for CMOS but also can be applied to photonics 13 and quantum computing 14 . Although we have thus far developed growth techniques for singlecrystalline CFAS layers on Ge 15 and Schottky-tunnel barrier electrodes with low values of the resistance area product (RA) for Ge spintronic devices 16 , the twoterminal MR ratio at room temperature has been quite low (≤0.001%) because of the low spin accumulation in Ge-based lateral spin-valve (LSV) devices 17 . When five-six atomic layers of Fe (Fe [5][6] ) are inserted between CFAS and Ge, we experimentally demonstrate salient enhancements in spin signals by more than one order of magnitude compared to those in the previous report on Ge 17 , in the LSV devices.…”

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confidence: 99%

Spin injection through energy-band symmetry matching with high spin polarization in atomically controlled ferromagnet/ferromagnet/semiconductor structures

et al. 2020

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Electrical injection of spin-polarized electrons from ferromagnets into semiconductors has been generally demonstrated through a tunneling process with insulator barrier layers that can dominate the device performance, including the electric power at the electrodes. Here, we show an efficient spin injection technique for a semiconductor using an atomically controlled ferromagnet/ferromagnet/semiconductor heterostructure with low-resistive Schottkytunnel barriers. On the basis of symmetry matching of the electronic bands between the top highly spin-polarized ferromagnet and the semiconductor, the magnitude of the spin signals in lateral spin-valve devices can be enhanced by up to one order of magnitude compared to those obtained with conventional ferromagnet/semiconductor structures. This approach provides a new solution for the simultaneous achievement of highly efficient spin injection and low electric power at the electrodes in semiconductor devices, leading to novel semiconductor spintronic architectures at room temperature.

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Half‐Metallic Heusler Alloy/GaN Heterostructure for Semiconductor Spintronics Devices

Yamada

Kato

Ichikawa

et al. 2023

Adv Elect Materials

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Because spin-orbit coupling in wurtzite semiconductors is relatively weak compared with that in zincblende ones, the III-nitride semiconductor GaN is a promising material for high-performance optical semiconductor spintronic devices such as spin lasers. For the purpose of reducing the operating power of spin lasers, it is necessary to demonstrate highly efficient electrical spin injection from a ferromagnetic material into GaN with a low-resistance contact. Here, an epitaxial half-metallic Heusler alloy Co 2 FeAl x Si 1−x (CFAS)/GaN heterostructure is developed by inserting an ultrathin Co layer between the CFAS and GaN. The CFAS/n + -GaN heterojunctions clearly show tunnel conduction with very small rectification and a low resistance-area product of ≈3.8 k𝛀μm 2 , which is several orders of magnitude smaller than those reported in previous work, at room temperature. Nonlocal spin signals and a Hanle effect curve are observed at low temperatures using lateral spin-valve devices with the CFAS/n + -GaN contacts, suggesting pure spin current transport in bulk GaN. The spin transport is observed at temperatures as high as room temperature, with a high spin polarization of 0.2 at a low bias voltage less than 2.0 V. This study is expected to open a path to GaN-based spintronic devices with highly spin-polarized and low-resistance contacts.

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Spin Transport and Relaxation up to 250 K in Heavily Doped n -Type Ge Detected Using Co2FeAl0.5

Cited by 55 publications

References 75 publications

Correlation between spin transport signal and Heusler/semiconductor interface quality in lateral spin-valve devices

Correlation between spin transport signal and Heusler/semiconductor interface quality in lateral spin-valve devices

Spin injection through energy-band symmetry matching with high spin polarization in atomically controlled ferromagnet/ferromagnet/semiconductor structures

Half‐Metallic Heusler Alloy/GaN Heterostructure for Semiconductor Spintronics Devices

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