Spin coherence and dephasing in GaN

Beschoten, Bernd; Johnston-Halperin, Ezekiel; Young, D. K.; Poggio, Martino; Grimaldi, J. E.; Keller, S.; DenBaars, Steven P.; Mishra, Umesh K.; Hu, Evelyn L.; Awschalom, D. D.

doi:10.1103/physrevb.63.121202

Cited by 202 publications

(149 citation statements)

References 23 publications

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“…Experimentally, long spin dephasing times of the average spin have been measured by different techniques for different materials and experimental conditions. 4,19 These include n-GaAs quantum wells with different widths, 5 doping levels, 7,17 materials, 18,20 as well as bulk n-GaAs. 21 In these experiments, spin lifetimes ranging from hundreds of picoseconds to tens of nanoseconds have been reported.…”

Section: ͑6͒mentioning

confidence: 99%

Optical manipulation of collective spin correlations in semiconductors with a squeezed vacuum of polarized photons

2008

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We calculate the transfer rate of correlations from polarization entangled photons to the collective spin of a many-electron state in a two-band system. It is shown that when a semiconductor absorbs pairs of photons from a two-mode squeezed vacuum, certain fourth-order electron-photon processes correlate the spins of the excited electron pairs of different quasimomenta. Different distributions of the quantum Stokes vector of the light lead to either enhancement or reduction of the collective spin correlations, depending on the symmetry of the distribution. We find that as the squeezing of the light becomes nonclassical, the spin correlations exhibit a crossover from being positive with an ϳN 2 ͑N is the average photon number͒ scaling to being negative with ϳN scaling, even when N is not small. Negative spin correlations mean a preponderance of spin singlets in the optically generated state. We discuss the possibility to measure the collective spin correlations through the measurement of the Faraday rotation fluctuation spectrum in a steady-state configuration.

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Section: ͑6͒mentioning

confidence: 99%

Optical manipulation of collective spin correlations in semiconductors with a squeezed vacuum of polarized photons

2008

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“…4 Previous studies on spin-relaxation mechanisms in GaN by optical measurements, such as time-resolved Faraday rotation and time-resolved Kerr rotation, have shown that the DP mechanism is the dominant spin-relaxation mechanism. 5,6 In this study we report electrical spin injection and detection in bulk w-GaN using an epitaxially grown MnAs/AlAs ferromagnetic tunnel contact in the three-terminal Hanle geometry. The measurements were carried out in a broad temperature range of 10-300 K and across several samples with different doping densities.…”

Section: Introductionmentioning

confidence: 99%

Spin diffusion in bulk GaN measured with MnAs spin injector

et al. 2012

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Spin injection and precession in bulk wurtzite n-GaN with different doping densities are demonstrated with a ferromagnetic MnAs contact using the three-terminal Hanle measurement technique. Theoretical analysis using minimum fitting parameters indicates that the spin accumulation is primarily in the n-GaN channel rather than at the ferromagnet (FM)/semiconductor (SC) interface states. Spin relaxation in GaN is interpreted in terms of the D'yakonov-Perel mechanism, yielding a maximum spin lifetime of 44 ps and a spin diffusion length of 175 nm at room temperature. Our results indicate that epitaxial ferromagnetic MnAs is a suitable high-temperature spin injector for GaN.

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“…For the GaAs (100) surface we observe an increase from about 60 ps to 1600 ps over an energy range of more than 0.3 eV, whereas the spin-relaxation time for the (011) surface is about 60 ps, independent of energy. The bulk spin relaxation was measured on an identical sample by means of the time-resolved magnetooptical Faraday effect [16,17]. The bulk spin-relaxation time was found to be 60 ps at room temperature regardless of the crystal orientation and is also shown in Figure 4 as a guide to the eye.…”

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Energy-resolved electron spin dynamics at surfaces ofp-doped GaAs

et al. 2006

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Electron-spin relaxation at different surfaces of p-doped GaAs is investigated by means of spin, time and energy resolved 2-photon photoemission. These results are contrasted with bulk results obtained by time-resolved Faraday rotation measurements as well as calculations of the Bir-Aronov-Pikus spin-flip mechanism. Due to the reduced hole density in the band bending region at the (100) surface the spin-relaxation time increases over two orders of magnitude towards lower energies. At the flat-band (011) surface a constant spin relaxation time in agreement with our measurements and calculations for bulk GaAs is obtained. PACS numbers: 72.25.Mk,72.25.Rb,78.47.+p In recent years, much experimental and theoretical work has been focused on the control and manipulation of the electronic spin degree of freedom independently of its charge, with the ultimate goal of spintronics devices, in which the electron spins are the carriers of the information [1]. The limiting factor for the usefulness of the information encoded in a spin-polarized current in a non-ferromagnetic semiconductor is the relaxation of the spin polarization, which is caused by a variety of interaction mechanisms [2]. In bulk GaAs, the relaxation of optically induced spin polarizations has been studied intensely for more than 30 years. Early work has led to the identification of several mechanisms that destroy the spin polarization, and good agreement between experiment and theory was found on the level of numerical and experimental accuracy available at that time [3]. In recent years, there has been renewed experimental and theoretical interest in spin relaxation, with many experimental studies focusing on undoped and n-doped semiconductors [4,5]. Early results for p-doped GaAs were obtained by means of hot photon luminescence and the Hanle effect [6]. Surfaces and interfaces, such as Schottky barriers, originally received comparatively little attention [7,8]. More recently, however, interfaces have been studied because of their importance for spintronics device applications where efficient electrical spin injection from a ferromagnetic metal or half-metal through a Schottky barrier into the semiconductor is of utmost importance [9]. The difficulty of efficient spin injection has stimulated interest in a fundamental understanding of spin-flip scattering at semiconductor surfaces and interfaces, e. g., at step edges [10].The purpose of this paper is the investigation of electron spin-relaxation in p-doped GaAs and the unambiguous identification of surface effects on the electron spin-relaxation. Using a spin, energy and time-resolved photoemission technique [11] we study the room-temperature spin-dependent electron dynamics at two surfaces with different characteristics [12]: the (100) surface with pronounced band-bending and the cleaved (011) surface, for which we expect flat-band conditions. To obtain a complete picture of the spin relaxation at surfaces as compared to the bulk we have also measured bulk spin relaxation-times by time-resolved Farada...

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Spin coherence and dephasing in GaN

Cited by 202 publications

References 23 publications

Optical manipulation of collective spin correlations in semiconductors with a squeezed vacuum of polarized photons

Optical manipulation of collective spin correlations in semiconductors with a squeezed vacuum of polarized photons

Spin diffusion in bulk GaN measured with MnAs spin injector

Energy-resolved electron spin dynamics at surfaces ofp-doped GaAs

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