Room-temperature spin transport in n-Ge probed by four-terminal nonlocal measurements

Yamada, Michihiro; Tsukahara, Makoto; Fujita, Y.; Naitô, Takeshi; Yamada, Shinya; Sawano, Kentarou; Hamaya, Kohei

doi:10.7567/apex.10.093001

Cited by 39 publications

(43 citation statements)

References 63 publications

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“…In the so-called nonlocal spin transport devices 19,20 , one employs a four-terminal measurement configuration in which one ferromagnetic contact is biased in order to induce a spin accumulation in the nonmagnetic channel, whereas the second ferromagnetic contact, the spin detector, remains unbiased. The spin signals observed in such nonlocal devices with tunnel contacts [21][22][23][24][25][26][27][28][29] are well described by the theory for spin injection and detection in the linear response regime 13,30 . Consequently, nonlocal devices have been instrumental to prove and understand spin injection and transport in a wide variety of materials, although they are of little direct technological relevance.…”

Section: Introductionmentioning

confidence: 74%

Nonlinear Electrical Spin Conversion in a Biased Ferromagnetic Tunnel Contact

et al. 2018

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The conversion of spin information into electrical signals is indispensable for spintronic technologies. Spin-to-charge conversion in ferromagnetic tunnel contacts is well-described using linear (spin-)transport equations, provided that there is no applied bias, as in nonlocal spin detection. It is shown here that in a biased ferromagnetic tunnel contact, spin detection is strongly nonlinear. As a result, the spin-detection efficiency is not equal to the tunnel spin polarization. In silicon-based 4-terminal spin-transport devices, even a small bias (tens of mV) across the Fe/MgO detector contact enhances the spin-detection efficiency to values up to 140 % (spin extraction bias) or, for spin injection bias, reduces it to almost zero, while, parenthetically, the charge current remains highly spin polarized. Calculations reveal that the nonlinearity originates from the energy dispersion of the tunnel transmission and the resulting nonuniform energy distribution of the tunnel current, offering a route to engineer spin conversion. Taking nonlinear spin detection into account is also shown to explain a multitude of peculiar and puzzling spin signals in structures with a biased detector, including two-and three-terminal devices, and provides a unified, consistent and quantitative description of spin signals in devices with a biased and unbiased detector.

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Section: Introductionmentioning

confidence: 74%

Nonlinear Electrical Spin Conversion in a Biased Ferromagnetic Tunnel Contact

et al. 2018

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“…Semiconductor (SC)-based spintronics has been explored for novel information storage and logic devices utilizing the spin angular momentum [1][2][3][4][5][6][7] . Recent works have clarified some important parameters such as spin lifetime and spin diffusion length in SCs by using fourterminal nonlocal measurements [8][9][10] , which are the most reliable methods, in lateral spin-valve (LSV) devices with GaAs 4,[11][12][13] , Si [14][15][16] , and Ge channels [17][18][19][20][21] .…”

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confidence: 99%

“…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.…”

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confidence: 99%

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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“…In the field of semiconductor-based spintronics, electrical spin injection and detection in GaAs have so far been demonstrated [ 6 , 7 , 8 , 9 ]. Taking the compatibility with existing Si-based electronic devices into consideration, it is important to electrically inject and detect spins in group-IV semiconductors such as Si [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ] and Ge [ 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ]. However, due to the large conductivity (spin resistance) mismatch between ferromagnet (FM) and semiconductor (SC) [ 28 ], it has been generally recognized that tunnel barriers should be inserted at the FM/SC interface for electrical spin injection and detection in SC [ 29 , 30 , 31 ].…”

Section: Introductionmentioning

confidence: 99%

Spin Absorption Effect at Ferromagnet/Ge Schottky-Tunnel Contacts

et al. 2018

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We study the influence of the junction size in ferromagnet (FM)/semiconductor (SC) contacts on four-terminal nonlocal spin signals in SC-based lateral spin-valve (LSV) structures. When we use FM/Ge Schottky-tunnel junctions with relatively low resistance-area products, the magnitude of the nonlocal spin signal depends clearly on the junction size, indicating the presence of the spin absorption effect at the spin-injector contact. The temperature-dependent spin signal can also be affected by the spin absorption effect. For SC spintronic applications with a low parasitic resistance, we should consider the influence of the spin absorption on the spin-transport signals in SC-based device structures.

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Room-temperature spin transport in n-Ge probed by four-terminal nonlocal measurements

Cited by 39 publications

References 63 publications

Nonlinear Electrical Spin Conversion in a Biased Ferromagnetic Tunnel Contact

Nonlinear Electrical Spin Conversion in a Biased Ferromagnetic Tunnel Contact

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

Spin Absorption Effect at Ferromagnet/Ge Schottky-Tunnel Contacts

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