Electrical spin injection and detection in lateral all-semiconductor devices

Ciorga, Mariusz; Einwanger, Andreas; Wurstbauer, Ursula; Schuh, Dieter; Wegscheider, Werner; Weiss, Dieter

doi:10.1103/physrevb.79.165321

Cited by 135 publications

(186 citation statements)

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“…This reference sample has been fabricated from the same wafer as the Fe coated 20 nm thick (Ga,Mn)As by covering one half of the ðGa; MnÞAs=GaAs wafer with a shutter while depositing Fe and Au on the other half. The H-field was oriented along [100], the easy axis of (Ga,Mn)As, and the data were taken at 50 K, shown without subtracting the characteristic offset, often found in nonlocal SV experiments [14,17]. The downward spike at zero field is found in all data at lower T and is caused by the polarized nuclei generated by the spin-polarized current across the Esaki diode [14,22,23].…”

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confidence: 99%

“…The 3-T voltage contains additional information on the interface resistance and tunnelling anisotropic magnetoresistance [14,20]. To unambiguously confirm spin injection we performed 3-T and nonlocal measurements also in a perpendicular H field, i.e., in Hanle geometry [14][15][16][17][18].…”

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confidence: 99%

“…n þ GaAs transition layer (n þ ¼ 5 Â 10 18 cm À3 ), 8 nm n þ -GaAs, and 2.2 nm low-temperature (LT)-grown Al 0:36 Ga 0:64 As, serving as a diffusion barrier, followed by LT-grown Ga 0:95 Mn 0:05 As, the thickness of which was chosen between 5 and 20 nm. The highly doped ðGa; MnÞAs=GaAs pn junction forms an Esaki diode [13,14]. In a next step the wafers were transferred, without breaking vacuum, into an attached metal-MBE chamber, where 2 nm of Fe, corresponding to 14 monolayers (MLs), were epitaxially grown at RT, and finally covered by 4 nm (20 MLs) of Au.…”

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confidence: 99%

“…A field offset due to the hysteresis of the superconducting coils was subtracted so that H ¼ 0 coincides with the depolarization peak. Voltages with H applied in-plane were either measured in nonlocal [14][15][16][17][18] …”

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Proximity Induced Enhancement of the Curie Temperature in Hybrid Spin Injection Devices

et al. 2011

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We investigate the increase of the Curie temperature T C in a lateral spin injection geometry where the ferromagnetic (Ga,Mn)As injector and detector contacts are capped by a thin iron film. Because of interlayer coupling between Fe and (Ga,Mn)As T C gets enhanced by nearly 100% for the thinnest (Ga,Mn)As films. The use of the proximity effect might pave the way for practical implementation of spintronic devices. DOI: 10.1103/PhysRevLett.107.056601 PACS numbers: 72.25.Àb, 75.30.Et, 75.50.Pp, 85.75.Àd The diluted magnetic semiconductor (DMS) (Ga,Mn)As [1] stands out as a seminal spintronic material due to its high spin polarization [2,3] and superior interfacing properties with nonmagnetic semiconductors. This opens a way to semiconducting spintronic devices with functionalities such as nonvolatility and the additional spin degree of freedom [4]. However, the persistently low Curie temperature of DMS has been an obstacle for the integration of DMS into electronic devices. It has been recently shown that the presence of a thin layer of Fe couples the magnetic moments of Fe and Mn in Fe=ðGa; MnÞAs bilayers up to room temperature (RT), thus well exceeding the T C of (Ga,Mn)As [5][6][7]. This proximity polarization leads to an antiparallel coupling of the Fe and Mn moments within an interfacial region of a few nm thickness in the (Ga,Mn)As film. In addition, exchange bias has been observed in the Fe=ðGa; MnÞAs bilayer system at lower temperatures T [7]. Similar exchange bias has been obtained in MnAs= ðGa; MnÞAs bilayers [8][9][10]. Differently, NiFe=ðGa; MnÞAs bilayers switch their magnetization independently [11] and also MnTe=ðGa; MnÞAs heterojunctions did not show exchange bias [12]. Here we use the interlayer coupling between Fe and (Ga,Mn)As to explore its impact on the operation temperature of (Ga,Mn)As based spin injector or detector contacts in a lateral transistorlike geometry.The experiments described below demonstrate enhanced spin injection temperatures measured in an all-electrical fashion.The heterojunctions were grown by molecular-beamepitaxy (MBE) on (001) GaAs substrates and consist of a 1000 nm thick n-type transport channel, doped with 4 Â 10 16 cm À3 Si, a 15 nm thin n ! n þ GaAs transition layer (n þ ¼ 5 Â 10 18 cm À3 ), 8 nm n þ -GaAs, and 2.2 nm low-temperature (LT)-grown Al 0:36 Ga 0:64 As, serving as a diffusion barrier, followed by LT-grown Ga 0:95 Mn 0:05 As, the thickness of which was chosen between 5 and 20 nm. The highly doped ðGa; MnÞAs=GaAs pn junction forms an Esaki diode [13,14]. In a next step the wafers were transferred, without breaking vacuum, into an attached metal-MBE chamber, where 2 nm of Fe, corresponding to 14 monolayers (MLs), were epitaxially grown at RT, and finally covered by 4 nm (20 MLs) of Au. The lateral channel of the devices was made by standard lithographic techniques. Electron beam lithography was used to pattern the Fe=ðGa; MnÞAs injector and detector contacts, oriented along the [110] direction, i.e., the easy axis of Fe. A schematic of the sample layout ...

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Proximity Induced Enhancement of the Curie Temperature in Hybrid Spin Injection Devices

et al. 2011

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“…spin accumulation) in nonmagnetic SC is a central issue of SC-based spintronics 1,[3][4][5] . Significant progress has been made on the spin accumulation in various SC systems by means of circularly polarized light 4,6 , spin-polarized tunneling [7][8][9][10][11][12][13] , hotelectron spin filtering 14,15 , spin-orbit interaction 16,17 , or magnetization dynamics 18,19 .…”

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Thermal Spin Injection and Accumulation in CoFe/MgO/n-type Ge Contacts

Jeon¹,

Min²,

Park³

et al. 2013

Extended Abstracts of the 2013 International Conference on Solid State Devices and Materials

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Understanding the interplay between spin and heat is a fundamental and intriguing subject. Here we report thermal spin injection and accumulation in CoFe/MgO/n-type Ge contacts with an asymmetry of tunnel spin polarization. Using local heating of electrodes by laser beam or electrical current, the thermally-induced spin accumulation is observed for both polarities of the temperature gradient across the tunnel contact. We observe that the magnitude of thermally injected spin signal scales linearly with the power of local heating of electrodes, and its sign is reversed as we invert the temperature gradient. A large Hanle magnetothermopower (HMTP) of about 7.0% and the Seebeck spin tunneling coefficient of larger than 0.74 meV K 21 are obtained at room temperature.T he tremendous power consumption and accompanying heat generation in current electronic devices requires alternative technologies to provide a solution for the energy issues and to realize the energy efficient electronics. Spintronics is a viable route for it, using the spin degree of freedom in addition to the conventional charge transport 1 . Recently another important ingredient, namely heat, appears on the stage. It has been reported that the temperature gradient and heat flow in ferromagnetic structures gives rise to a variety of spin related phenomena 2 . Understanding the interplay between heat and spin transport is a fundamental and intriguing subject but also offers unique possibilities for emerging electronics based on the combination of thermoelectrics and spintronics.Especially in SC-based spintronics, the functional use of heat provides a new route to inject and control of spin in semiconductors (SCs) 3 . The generation of non-equilibrium spin populations (i.e. spin accumulation) in nonmagnetic SC is a central issue of SC-based spintronics 1,3-5 . Significant progress has been made on the spin accumulation in various SC systems by means of circularly polarized light 4,6 , spin-polarized tunneling 7-13 , hotelectron spin filtering 14,15 , spin-orbit interaction 16,17 , or magnetization dynamics 18,19 .Intriguingly, Le Breton et al. 20 have reported a rather different mechanism for the spin accumulation, in which temperature difference across a ferromagnet (FM)/oxide/SC tunnel contact can induce the spin accumulation (Dm) in SC via Seebeck spin tunneling (SST). It was found that the SST effect, involving thermal transfer of spin angular momentum from FM to SC without a tunneling charge current, is a purely interface-related phenomenon of the tunnel contact and governed by the energy dependence of its tunnel spin polarization (TSP) 20 . This provides a conceptually new mechanism for the generation of Dm in SC as well as for the functional use of heat in spintronic devices 20 . The SST and thermal spin accumulation (Dm th ) in p-type SC (e.g., p-type Si) have been intensely studied, using a Ni 80 Fe 20 /Al 2 O 3 /SiO 2 /p-SC contact with the asymmetry in TSP of tunneling holes 20 . However, the counterpart of n-type SC still needs to be explored...

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Chirality‐Induced Magnet‐Free Spin Generation in a Semiconductor

Liu,

Adhikari,

Wang

et al. 2024

Advanced Materials

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Electrical generation and transduction of polarized electron spins in semiconductors are of central interest in spintronics and quantum information science. While spin generation in semiconductors has been frequently realized via electrical injection from a ferromagnet, there are significant advantages in nonmagnetic pathways of creating spin polarization. One such pathway exploits the interplay of electron spin with chirality in electronic structures or real space. Here, utilizing chirality‐induced spin selectivity (CISS), we demonstrate efficient creation of spin accumulation in n‐doped GaAs via electric current injection from a normal metal (Au) electrode through a self‐assembled monolayer of chiral molecules (α‐helix L‐polyalanine, AHPA‐L). The resulting spin polarization is detected as a Hanle effect in the n‐GaAs, which is found to obey a distinct universal scaling with temperature and bias current consistent with chirality‐induced spin accumulation. The experiment constitutes a definitive observation of CISS in a fully nonmagnetic device structure and demonstration of its ability to generate spin accumulation in a conventional semiconductor. The results thus place key constraints on the physical mechanism of CISS and present a new scheme for magnet‐free semiconductor spintronics.This article is protected by copyright. All rights reserved

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Electrical spin injection and detection in lateral all-semiconductor devices

Cited by 135 publications

References 32 publications

Proximity Induced Enhancement of the Curie Temperature in Hybrid Spin Injection Devices

Proximity Induced Enhancement of the Curie Temperature in Hybrid Spin Injection Devices

Thermal Spin Injection and Accumulation in CoFe/MgO/n-type Ge Contacts

Chirality‐Induced Magnet‐Free Spin Generation in a Semiconductor

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