Built-in electric-field effects in wurtzite AlGaN/GaN quantum wells

Grandjean, N.; Damilano, B.; Dalmasso, S.; Leroux, M.; Laügt, M.; Massies, J.

doi:10.1063/1.371241

Cited by 261 publications

(167 citation statements)

References 21 publications

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“…We note that the theoretical α e values are in the same order of magnitude of the effective Rashba coupling measured on AlGaN/GaN [27]. Since the magnitude of the in-plane strain in InGaN/GaN is close to that in AlGaN/GaN, the magnitude of built-in electric field is found to be in the same order of magnitude in both systems (∼ 1M V /cm) [28,29]. Therefore, we may expect InGaN/GaN and AlGaN/GaN to have similar coupling parameters α e and β, and hence the the-oretical α e and β (Fig.…”

supporting

confidence: 67%

Erratum: Current and Strain-Induced Spin Polarization inInGaN/GaNSuperlattices [Phys. Rev. Lett.98, 136403 (2007)]

Chang¹,

Chen²,

Chen³

et al. 2007

Phys. Rev. Lett.

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The lateral current-induced spin polarization in InGaN/GaN superlattices (SLs) without an applied magnetic field is reported. The fact that the sign of the nonequilibrium spin changes as the current reverses and is opposite for the two edges provides a clear signature for the spin Hall effect. In addition, it is discovered that the spin Hall effect can be strongly manipulated by the internal strains. A theoretical work has also been developed to understand the observed strain induced spin polarization. Our result paves an alternative way for the generation of spin polarized current.PACS numbers: 72.25.Dc, 78.20.Hp, 78.55.Cr It has been proposed theoretically that a transverse spin current, the so called spin Hall current, can be generated in strongly spin-orbit coupling systems by external electric field [1,2,3,4,5,6,7]. This novel phenomenon offers the exciting possibility of pure electric driven spintronics in semiconductors, which can be more readily integrated with current industry. Recently, the observations of the spin Hall effect have been reported [8,9,10] in GaAs based devices, which has generated an intensive research [11,12,13,14,15,16]. However, up to now, most of the experimental measurements were concentrated on GaAs system. More clear evidences to confirm the spin Hall effect in other semiconductors are still needed [17]. Nitride semiconductors probably represent the most studied material system in semiconductor community for the last decade. InGaN/GaN superlattices have become particularly attractive because of their wide applications in light-emitting diodes (LEDs) [18] and high efficiency laser diodes (LDs) [19]. In this letter, we provide the first experimental observation of currentinduced spin polarization in InGaN/GaN superlattices. In addition, we discover that the spin Hall effect can be strongly manipulated by the internal strains. In order to have a fundamental understanding of the strain-induced spin Hall effect, a theoretical investigation has also been performed. Because strains are commonly present in semiconductor multilayers and superlattices due to lattice mismatch, our result therefore provides a convenient way to control the magnitude of the spin Hall effect, which should be very useful for the future applications. Furthermore, this strain dependence enables to resolve the intensive debate about whether the intrinsic spin Hall effect remains valid beyond the ballistic transport regime.The n-type InGaN/GaN superlattices were grown by a horizontal flow metalorganic chemical vapor deposition on (0001) sapphire substrate. All structures consist of 30 nm buffer layer, followed by a 2 µm epitaxial GaN layer and then 50 periods of InGaN/GaN superlattices. Superlattices are composed of periods of alternating 30Å GaN barriers and 50Å In x Ga 1−x N wells with x ∼ 0.15. The superlattices was doped with Si, and the electron concentration is 2x10 12 cm −2 according to the Hall measurement. For the cross sectional photoluminescence (PL) measurement, the sample was excited by a He-Cd lase...

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supporting

confidence: 67%

Erratum: Current and Strain-Induced Spin Polarization inInGaN/GaNSuperlattices [Phys. Rev. Lett.98, 136403 (2007)]

Chang¹,

Chen²,

Chen³

et al. 2007

Phys. Rev. Lett.

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“…The high quality of homoepitaxial samples has already been demonstrated by the small photoluminescence linewidth ͑15-20 meV͒ measured on GaN/AlGaN quantum wells deposited using the same growth conditions. 10 Figure 1 shows the Hall mobility H ͓Fig. 1͑a͔͒ and the Hall carrier density n H ͓Fig.…”

mentioning

confidence: 99%

High electron mobility in AlGaN/GaN heterostructures grown on bulk GaN substrates

Frayssinet

Knap

Lorenzini

et al. 2000

Applied Physics Letters

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128

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Dislocation-free high-quality AlGaN/GaN heterostructures have been grown by molecular-beam epitaxy on semi-insulating bulk GaN substrates. Hall measurements performed in the 300 K–50 mK range show a low-temperature electron mobility exceeding 60 000 cm2/V s for an electron sheet density of 2.4×1012 cm−2. Magnetotransport experiments performed up to 15 T exhibit well-defined quantum Hall-effect features. The structures corresponding to the cyclotron and spin splitting were clearly resolved. From an analysis of the Shubnikov de Hass oscillations and the low-temperature mobility we found the quantum and transport scattering times to be 0.4 and 8.2 ps, respectively. The high ratio of the scattering to quantum relaxation time indicates that the main scattering mechanisms, at low temperatures, are due to long-range potentials, such as Coulomb potentials of ionized impurities.

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“…Finally, we assign the emission lines around 3.560 and 3.48 eV to the luminescence of the 5% Al x Ga 1 À x N barriers and the GaN buffer layer, respectively. Owing to the presence of intrinsic polarization fields in c-planeoriented III-nitride heterostructures that lead to the quantumconfined Stark effect, the e-h wavefunction overlap may be markedly reduced in such QWs 16 . This effect is most prominent for low carrier densities, while increasing the latter will progressively screen the polarization field.…”

Section: Resultsmentioning

confidence: 99%