Initial/final state selection of the spin polarization in electron tunneling across an epitaxial Fe∕GaAs(001) interface

Kurebayashi, Hidekazu; Steinmüller, S. J.; Laloe, J.‐B.; Trypiniotis, T.; Easton, S.; Ionescu, Adrian M.; Yates, Jonathan R.; Bland, J. A. C.

doi:10.1063/1.2783187

Cited by 23 publications

(20 citation statements)

References 13 publications

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“…This obstacle can be removed by inserting a tunneling spin-polarized slab between the FM and SC interfaces. Such a tunneling slab can be either an intrinsic Schottky barrier 2,3 or an extrinsic tunneling barrier. 4,5 An alternative approach is to attempt to mimic the extraordinary success of spin-polarized tunneling in Fe/ MgO/Fe junctions and work in the ballistic regime.…”

Section: Introductionmentioning

confidence: 99%

Theory of tunneling magnetoresistance of Fe/GaAs/Fe(001) junctions

2010

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We investigate theoretically spin-dependent transport through an epitaxial Fe/GaAs/Fe͑001͒ tunnel junction with and without spin-orbit interaction. Calculations neglecting spin-orbit interaction and the effect of d orbitals on the GaAs band structure predict that the tunneling magnetoresistance ͑TMR͒ should increase with increasing thickness of GaAs barrier and approach values close to the perfect spin-valve limit. However, when d orbitals and, in particular, spin-orbit interaction is included the TMR ratio saturates rapidly with GaAs thickness to a rather modest value of about 30% when the Fermi level E F lies in the middle of the GaAs gap. This unexpectedly small value cannot be explained by spin-orbit interaction alone. It is shown that the underlying reason for this is the presence of a resonance in the minority-spin band structure of the Fe/GaAs/Fe trilayer lying close to the center of the gap. Investigation of the dependence of the TMR on the height of the GaAs barrier ͑position of the Fermi energy E F in the gap͒ shows that the TMR of a perfect junction is strongly enhanced when E F lies at the resonance in the minority-spin channel. However, we show that any small asymmetry of the junction removes the TMR peak and reduces the TMR to small values, of the order of 50%, for a rather large interval of values of E F in the vicinity of the middle of the GaAs gap. We thus conclude that the spin-orbit coupling leads to saturation of the TMR with GaAs thickness, but the saturation value is determined by the presence of the resonance.

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Section: Introductionmentioning

confidence: 99%

Theory of tunneling magnetoresistance of Fe/GaAs/Fe(001) junctions

2010

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“…Since that fi rst experiment, there have been many related studies [16,[24][25][26][75][76][77][78][79][80][81][82][83][84][85][86]. Taniyama et al [78], Steinmuller et al [79] and Park et al [86] measured the spin-dependent photocurrent for Fe/AlO x /GaAs, NiFe(Fe)/GaAs and Fe/MgO/GaAs interfaces, respectively, under forward bias with optical spin orientation.…”

Section: Experimental Studies Of Spin Transport Into Ferromagnetsmentioning

confidence: 99%

Electrical and optical spin injection in ferromagnet/semiconductor heterostructures

et al. 2011

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T he operation of the rapidly expanding range of electronic devices, such as personal computers and mobile phones, is primarily based on the control of electron charge in semiconductors. Although the tremendous progress in microfabrication technologies has accelerated the miniaturization of electronic devices, the size of devices will soon encounter the fundamental physical limits of that miniaturization. Further scale reduction beyond these limits will require a radical alteration of the concept of functional devices. Control of the spin degree of freedom of an electron has brought about a new era of integration in electronics over the last ten years, and research in the fi eld of 'spintronics' is currently being pursued extensively due to the potential of this approach for the development of a new direction in electronics. Th e fi eld of spintronics spreads beyond the traditional boundaries among research fi elds, leading to interdisciplinary research that spans magnetism, semiconductors, photonics and electronics.Since 1990, a number of spin-based device concepts have been proposed. Spin-based transistors [1][2][3][4][5], spin light-emitting diodes (spin-LEDs) [6,7] and spin transfer torque memories [8,9] are typical examples. One of the device concepts is depicted in Figure 1, where the device structure consists of a ferromagnetic source electrode, a highmobility semiconductor channel, a ferromagnetic drain electrode and a gate electrode. To operate a spin-based functional device, the primary issue is the effi cient injection of spin-polarized electrons from the source ferromagnet into the semiconductor channel across the interface. Th e electron spin is then manipulated by the application of a voltage via the gate electrode [10], and the spin orientation is detected using a ferromagnetic drain electrode in a spin fi eld-eff ect transistor (FET) or from the circular polarization of light emission in a spin-LED. Although the device concept is very simple and similar to that of a conventional FET, the implementation of spin-based devices is not that straightforward: the spin degree of freedom must be handled very delicately because the spin current rapidly depolarizes at the ferromagnet/semiconductor interface and the spin information will be lost within a time scale of several hundred picoseconds, even in a semiconductor [11,12]. Th is is in clear contrast to the conservation of electron charge. Th erefore, there are still obstacles to overcome in the implementation of such spintronic devices, and for this purpose a clear understanding of not only electron spin transport processes from a ferromagnet into a semiconductor, and vice versa, but also electron spin dynamics in semiconductors, is of fundamental and technological importance.Our focus in this article is on reviewing the current status of this subject with special emphasis on electrical and optical spin injection Spin-based electronics or 'spintronics' is a rapidly expanding research area that off ers the promise of surpassing the limits of conventiona...

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“…By varying these parameter values, we fit the calculations to experimental data of the spin filtering effect (∆I SF ) [20], results of which are shown in Fig. 9.…”

Section: Comparison With Experimental Observationmentioning

confidence: 99%

“…In order to calculate electrons travelling across an epitaxial Fe/GaAs(001) interface, the spin polarisation of Fe for our model is calculated by integrating DOS of bulk bcc Fe band structure along the electron transport orientation. The Fe bulk DOS was calculated by density functional theory with a generalized gradient approximation [17,18,19,20]. These DOS for up-spin (N F e↑ ) and for down-spin (N F e↓ ) are shown in Fig.…”

Section: Tunnel Probability Through the Schottky Barrier And Fe Spin mentioning

confidence: 99%

Numerical calculation model for spin-dependent transport of photoexcited electrons across Fe/GaAs(0 0 1) interfaces

Kurebayashi¹,

Trypiniotis²,

Lee³

et al. 2010

J. Phys. D: Appl. Phys.

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Abstract. Spin-dependent transport of photogenerated electrons across Fe/GaAs(001) interfaces is calculated using a one-dimensional electron transport model. Creation of spin-polarised electrons by photoexcitation in this model is defined by the band structure of GaAs along the [001] direction and the optical selection rules. The tunnel probability across the interface is obtained from Chang's model and first principles calculations are employed to calculate the spin polarisation of Fe for electrons propagating along the [001] direction. By combining the above ingredients, the spin filtering current, I SF , was calculated for different parameter values, including Schottky barrier height and photon energy. The model is used to fit with experimental results of the photoexcitation technique, yielding qualitative agreement especially for the observed sign switching of the spin filtering current.

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Initial/final state selection of the spin polarization in electron tunneling across an epitaxial Fe∕GaAs(001) interface

Cited by 23 publications

References 13 publications

Theory of tunneling magnetoresistance of Fe/GaAs/Fe(001) junctions

Theory of tunneling magnetoresistance of Fe/GaAs/Fe(001) junctions

Electrical and optical spin injection in ferromagnet/semiconductor heterostructures

Numerical calculation model for spin-dependent transport of photoexcited electrons across Fe/GaAs(0 0 1) interfaces

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