Electron spin lifetimes in long-wavelength<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Hg</mml:mi></mml:mrow><mml:mrow><mml:mn>1</mml:mn><mml:mi>−</mml:mi><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Cd</mml:mi></mml:mrow><mml:mrow><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:mrow><mml:mi mathvariant="normal">Te</mml:mi></mml:math>and InSb at elevated tem

Murzyn, P.; Pidgeon, C. R.; Phillips, P. J.; Wells, J.‐P. R.; Gordon, Neil T.; Ashley, T.; Jefferson, J. H.; Burke, T. M.; Giess, J.; Merrick, M.; Murdin, B. N.; Maxey, C. D.

doi:10.1103/physrevb.67.235202

Cited by 22 publications

(17 citation statements)

References 16 publications

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“…In contrast to GaAsbased systems, relatively little attention has been paid to InAs, even although it may be important in future spintronics applications. We previously measured spin lifetimes in narrow-gap semiconductors ͑NGSs͒, Hg 1Ϫx Cd x Te and InSb, at wavelengths between 4 and 10 m over the temperature range of 4 to 300 K. 4 We have now extended those measurements to include bulk epilayers of InAs as a function of doping at 300 K.The 4,6,7 which excites spins in the semiconductor with above-bandgap, circularly polarized light, and probes the induced bleaching with either the same or the opposite circularly polarized light ͑SCP or OCP, respectively͒. The pump and probe beams are pulsed, and by changing the time delay between the pump and probe, and comparing the SCP and OCP results, we measure the spin decay lifetime.…”

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Suppression of D’yakonov–Perel spin relaxation in InAs and InSb by n-type doping at 300 K

Murzyn

Pidgeon

Phillips

et al. 2003

Applied Physics Letters

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We have made direct pump-probe measurements of spin lifetimes in intrinsic and degenerate n-InAs at 300 K. In particular, we measure remarkably long spin lifetimes ( s ϳ1.6 ns) for near-degenerate epilayers of n-InAs. For intrinsic material, we determine s ϳ20 ps, in agreement with other workers. There are two main models that have been invoked for describing spin relaxation in narrow-gap semiconductors: the D'yakonov-Perel ͑DP͒ model and the Elliott-Yafet ͑EY͒ model. For intrinsic material, the DP model is believed to dominate in III-V materials above 77 K, in agreement with our results. We show that in the presence of strong n-type doping, the DP relaxation is suppressed both by the degeneracy condition and by electron-electron scattering, and that the EY model then dominates for the n-type material. We show that this same process is also responsible for a hitherto unexplained lengthening of s with n-type doping in our earlier measurements of n-InSb. Utilization of the electron spin has become a focus of interest in semiconductor electronics, or spintronics, in recent years, and it is important to realize a sufficiently long spin lifetime s to process information stored in the form of the polarization of spin ensembles.1-3 To find a way to control s , it is necessary to understand the spin relaxation mechanisms in both bulk and low-dimensional semiconductor structures which are designed so that spins can be appropriately confined and/or transferred. In contrast to GaAsbased systems, relatively little attention has been paid to InAs, even although it may be important in future spintronics applications. We previously measured spin lifetimes in narrow-gap semiconductors ͑NGSs͒, Hg 1Ϫx Cd x Te and InSb, at wavelengths between 4 and 10 m over the temperature range of 4 to 300 K. 4 We have now extended those measurements to include bulk epilayers of InAs as a function of doping at 300 K.The 4,6,7 which excites spins in the semiconductor with above-bandgap, circularly polarized light, and probes the induced bleaching with either the same or the opposite circularly polarized light ͑SCP or OCP, respectively͒. The pump and probe beams are pulsed, and by changing the time delay between the pump and probe, and comparing the SCP and OCP results, we measure the spin decay lifetime. The optical pulses for the experiment, carried out at the University of Surrey, were generated with a solidstate laser system that produces ϳ40 fs pulses from 2.5 to 11 m wavelength, with a repetition rate of 250 kHz and typical average power of 5 mW. The beams were focused onto the sample with spot sizes of approximately 100 m, and the transmitted probe light was detected with a liquid-nitrogencooled InSb photodiode.Results for the transmission change in the probe due to the pump are shown for sample IC313 in Fig. 1 for SCP and OCP configurations at a wavelength of 3.4 m; that is, just above the absorption edge. The data are in extremely good agreement with the results of other workers.6 Following Ref. 6, we plot the fractional difference in tr...

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Suppression of D’yakonov–Perel spin relaxation in InAs and InSb by n-type doping at 300 K

Murzyn

Pidgeon

Phillips

et al. 2003

Applied Physics Letters

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“…In spite of their potential, many fewer time-resolved optical measurements of spin relaxation in narrow gap materials have been described than in the GaAs system, because of the relative rarity of suitable long wavelength short pulse light sources. However, we and others have reported such measurement of lifetimes in HgCdTe [9], InSb [9], InAs [10 -12], and InAs=GaSb superlattices [13]. For the same reason, to our knowledge, there have not been any reports of timeresolved monopolar excitation.…”

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“…1. At room temperature and zero magnetic field spin lifetimes of the order of 1 ns were reported for GaAs [22] (though of the order of hundreds of ns for low temperature), and 10 -20 ps for lightly n-type InSb and InAs [9][10][11][12], and have been interpreted with the DP mechanism. The expected difference in the DP lifetime between InSb and GaAs may be roughly estimated from band structure parameters at the band edge, since at the band edge where the spin splitting is cubic in k, m e = 3 ÿ p , where…”

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Spin Relaxation by Transient Monopolar and Bipolar Optical Orientation

et al. 2006

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We have used two-color time-resolved spectroscopy to measure the relaxation of electron spin polarizations in a bulk semiconductor. The circularly polarized pump beam induces a polarization either by direct excitation from the valence band, or by free-carrier (Drude) absorption when tuned to an energy below the band gap. We find that the spin relaxation time, measured with picosecond time resolution by resonant induced Faraday rotation in both cases, increases in the presence of photogenerated holes. In the case of the material chosen, n-InSb, the increase was from 14 to 38 ps. DOI: 10.1103/PhysRevLett.96.096603 PACS numbers: 72.25.Rb, 72.25.Fe, 78.47.+p Spin polarizations have become a focus of interest in semiconductor physics in recent years, not least for their potential application in ''spintronic'' devices [1]. It has been shown that spin polarized electrons (or holes) can be injected from magnetic semiconductor materials into semiconductors [2,3], that they can be coherently transported through a device [4], and that they can be controlled (or modulated) with an external electric field [5]. It remains challenging to improve these breakthroughs to the extent that they can be combined in a practical device [1]. A sufficiently long spin lifetime s is important in the design of structures which confine and/or transfer spin. It is therefore necessary to understand the establishment of a polarized spin population and subsequent spin relaxation mechanisms in both bulk and low dimensional semiconductors. A large amount of literature has been established to determine spin lifetimes by one or another form of timeresolved optical orientation techniques based on spin injection by pulsed interband pumping with circularly polarized light [4 -13]. In this Letter we investigate and contrast the spin relaxation lifetimes as measured in a bipolar (interband) experiment with spin lifetimes measured in a monopolar regime. In the former, significant numbers of excess electrons and holes are photopumped, whereas most device proposals involve electrical injection and manipulation of one type of charge carrier only, ideally at room temperature and often zero magnetic field. To this end we compare in such conditions the results of interband versus intraband pumping of spins with picosecond pulses, in the same sample. We find that the difference is a factor of between 2 to 3.Only one previous experiment measured the lifetime of spins pumped with monopolar excitation in zero magnetic field. In that case hole lifetimes in p-type GaAs=AlGaAs quantum wells were measured at low temperature by steady state bleaching of the circularly polarized photocurrent response [14]. The spin lifetime estimated from the saturation intensity was found to be 20 ps at liquid helium temperature. Our picosecond time-resolved measurements do not rely on theoretically derived absorption cross sections, were made on material at room temperature, and directly compare the bipolar and monopolar spin excitation and relaxation in the same sample. Our results...

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“…High mobility thin InSb is also interesting for spintronic applications because of the high spin-orbit coupling and large electron g factor ͑Ϫ50.6͒. Recent measurements of the spin lifetime 3 in n-type degenerate epilayers of InSb are encouraging, suggesting a RT spin lifetime of the order of 300 ps.…”

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High-mobility thin InSb films grown by molecular beam epitaxy

Zhang

Clowes

Debnath

et al. 2004

Applied Physics Letters

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The problem of preparing high-mobility thin InSb films is revisited for magnetoresistive and spintronic sensor applications. We introduce a growth process that significantly improves the electrical properties of thin unintentionally doped InSb layers ͑60-300 nm͒ epitaxially grown on GaAs͑100͒ substrates by reducing the density of dislocations within the interfacial layer. The epilayer properties are well described by a differential two-layer model. This model confirms that the contribution of the interface can only be donor-like. Moreover, the electrical properties of the InSb layers change continuously away from the interface up to sample thickness of the order of 1 m.

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Electron spin lifetimes in long-wavelengthHg1−xCdxTeand InSb at elevated tem

Cited by 22 publications

References 16 publications

Suppression of D’yakonov–Perel spin relaxation in InAs and InSb by n-type doping at 300 K

Suppression of D’yakonov–Perel spin relaxation in InAs and InSb by n-type doping at 300 K

Spin Relaxation by Transient Monopolar and Bipolar Optical Orientation

High-mobility thin InSb films grown by molecular beam epitaxy

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