Spin-dependent transport in metal/semiconductor tunnel junctions

Prins, Mwj Menno; Kempen, H. van; Leuken, H. van; Groot, de Robert; Roy, W. Van; Boeck, J. De

doi:10.1088/0953-8984/7/49/010

Cited by 64 publications

(53 citation statements)

References 50 publications

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“…2͒, we obtain a relative spin splitting of ͉⌬V s spin /V s ͉ϭ͑4Ϯ3͒ ϫ10 Ϫ2 or larger. Note that this value is close to the experimental result 16 obtained with planar junctions of Al 2 O 3 and Co.…”

Section: Discussionsupporting

confidence: 91%

“…14 In planar Co/Al 2 O 3 /GaAs junctions, evidence for spin-polarized tunneling of optically excited electrons was already reported. 15,16 The application of GaAs for magnetic imaging has become a hot issue with the development of cleaved GaAs tips for STM operation, under ultrahigh vacuum conditions, 17 as well as under ambient conditions. 18,19 In the latter studies, optical excitation was already included, but the spin sensitivity of GaAs tips was not yet demonstrated.…”

Section: Introductionmentioning

confidence: 99%

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Spin-polarized tunneling with GaAs tips in scanning tunneling microscopy

1996

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We describe a model as well as experiments on spin-polarized tunneling with the aid of optical spin orientation. This involves tunnel junctions between a magnetic material and gallium arsenide ͑GaAs͒, where the latter is optically excited with circularly polarized light in order to generate spin-polarized carriers. We present a transport model that takes account of carrier capture in the semiconductor surface states, and describes the semiconductor surface in terms of a spin-dependent energy distribution function. The so-called surface spin splitting can be calculated from the balance of the polarized electron and hole flow in the semiconductor subsurface region, the polarized tunneling current across the tunnel barrier between the magnetic material and the semiconductor surface, and the spin relaxation at the semiconductor surface. We present experimental data obtained in a scanning tunneling microscope with a GaAs tip and a Pt/Co multilayer sample under ambient conditions. A helicity asymmetry of tunnel current ͑i.e., a circular-polarization-dependent tunnel current͒ was found with a magnitude of 4 pA , which was verified not to be due to variations of the optical power. According to our model and estimations, this observation can be explained by spin-polarized tunneling, with a lower limit to the semiconductor surface spin splitting and spin lifetime of 4 mV and 0.4 ns, respectively.

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Section: Discussionsupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Spin-polarized tunneling with GaAs tips in scanning tunneling microscopy

1996

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“…There was no preferential behavior for spin injection using different azimuthal orientations of the epitaxial MnAs layer, which could have been expected from the symmetry between the conduction-band wave functions in MnAs and GaAs. The tunneling properties of a Schottky barrier were discussed by Meservey et al (1982); Gibson and Meservey (1985); Prins et al (1995);and Kreuzer et al (2002). The measured I-V curves display a complicated behavior (Hirohata et al, 2001;Isaković et al, 2001) which can be significantly affected by the interface (midgap) states at the Schottky barrier (Jonker et al, 1997).…”

Section: Metallic Ferromagnet/semiconductor Junctionsmentioning

confidence: 99%

Spintronics: Fundamentals and applications

2004

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Spintronics, or spin electronics, involves the study of active control and manipulation of spin degrees of freedom in solid-state systems. This article reviews the current status of this subject, including both recent advances and well-established results. The primary focus is on the basic physical principles underlying the generation of carrier spin polarization, spin dynamics, and spin-polarized transport in semiconductors and metals. Spin transport differs from charge transport in that spin is a nonconserved quantity in solids due to spin-orbit and hyperfine coupling. The authors discuss in detail spin decoherence mechanisms in metals and semiconductors. Various theories of spin injection and spin-polarized transport are applied to hybrid structures relevant to spin-based devices and fundamental studies of materials properties. Experimental work is reviewed with the emphasis on projected applications, in which external electric and magnetic fields and illumination by light will be used to control spin and charge dynamics to create new functionalities not feasible or ineffective with conventional electronics. CONTENTS

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“…6,7 For the STM geometry, a number of experiments supporting the feasibility of the method have been conducted. 8,9 Theoretical descriptions of spin-polarized transport in ferromagnet/semiconductor junctions also have been given.…”

Section: Introductionmentioning

confidence: 99%

Theory of spin-polarized transport in photoexcited semiconductor/ferromagnet tunnel junctions

1998

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We present a theory for spin-polarized transport in tunnel junctions consisting of a ferromagnet and a semiconductor, in which spin-polarized carriers are created by optical orientation. The model includes, for both spin orientations, the current due to tunneling between the ferromagnet and the semiconductor surface as well as the photoinduced and the thermionic emission currents through the semiconductor subsurface region. Tunneling is described in terms of a spin-dependent tunnel conductance, taking account of the magnetic structure of the ferromagnet. We consider spin depolarization of photoexcited electrons in the semiconductor bulk material and in surface states that have a spin-dependent occupation. The total tunnel current is evaluated as well as current modulations due to modulated spin polarization of photoelectrons ͑CPM signal͒ or modulated optical intensity. The calculations show that the CPM signal is proportional to the tunnel conductance polarization and is relatively insensitive to spin depolarization of photoelectrons during their transport to the surface. A severe signal reduction can, however, result from spin relaxation in semiconductor surface states. In addition, it is demonstrated that a crucial role is played by the operating regime of the junction, i.e., photoamperic or photovoltaic, where the selection is determined mainly by the choice of applied bias voltage. We find that the photovoltaic mode is favored, as it yields the highest contribution from spin-polarized tunneling, combined with the smallest sensitivity for unwanted light intensity modulations. ͓S0163-1829͑98͒03207-X͔

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Spin-dependent transport in metal/semiconductor tunnel junctions

Cited by 64 publications

References 50 publications

Spin-polarized tunneling with GaAs tips in scanning tunneling microscopy

Spin-polarized tunneling with GaAs tips in scanning tunneling microscopy

Spintronics: Fundamentals and applications

Theory of spin-polarized transport in photoexcited semiconductor/ferromagnet tunnel junctions

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