Magnetotransport in p-type Ge quantum well narrow wire arrays

Newton, Peter; Llandro, J.; Mansell, Rhodri; Holmes, S. N.; Morrison, C.; Foronda, Jamie; Myronov, Maksym; Leadley, D. R.; Barnes, C. H. W.

doi:10.1063/1.4919053

Cited by 6 publications

(9 citation statements)

References 32 publications

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“…[1][2][3][4][5][6][7][8][9][10][11] In germanium, the Dyakonov-Perel spin relaxation mechanism is suppressed by the inversion symmetry of the germanium crystal and the influence of the hyperfine interaction is minimal because of the zero nuclear spin of germanium's most abundant isotopes.…”

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confidence: 99%

Weak localization and weak antilocalization in doped germanium epilayers

Newton

Mansell

Holmes

et al. 2017

Applied Physics Letters

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The magnetoresistance of 50 nm thick epilayers of doped germanium is measured at a range of temperatures down to 1.6 K. Both n- and p-type devices show quantum corrections to the conductivity in an applied magnetic field, with n-type devices displaying weak localization and p-type devices showing weak antilocalization. From fits to these data using the Hikami-Larkin-Nagaoka model, the phase coherence length of each device is extracted, as well as the spin diffusion length of the p-type device. We obtain phase coherence lengths as large as 325 nm in the highly doped n-type device, presenting possible applications in quantum technologies. The decay of the phase coherence length with temperature is found to obey the same power law of lϕ ∝ Tc, where c = −0.68 ± 0.03, for each device, in spite of the clear differences in the nature of the conduction. In the p-type device, the measured spin diffusion length does not change over the range of temperatures for which weak antilocalization can be observed. The presence of a spin-orbit interaction manifested as weak antilocalization in the p-type epilayer suggests that these structures could be developed for use in spintronic devices such as the spin-FET, where significant spin lifetimes would be important for efficient device operation.

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confidence: 99%

Weak localization and weak antilocalization in doped germanium epilayers

Newton

Mansell

Holmes

et al. 2017

Applied Physics Letters

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“…Recent measurements on Ge quantum wells have however indicated either a weak structural inversion asymmetry (SIA)-induced, cubic Rashba spin-orbit coupling effect due to electric fields in the growth direction [6][7][8][9] or a Zeeman effect. 10 These measurements were carried out at a higher carrier density than reported in this work. There is a fundamental difference between zero magnetic field spin-splitting with no overall spin-polarization and spin-splitting in a finite magnetic field.…”

Section: Introductionmentioning

confidence: 98%

“…20 The effect is clearer in lower mobility material with larger Landau level broadening and is relatively unnoticed when p is >1.7 Â 10 11 cm À2 . At $2 Â 10 11 cm À2 in the modulation doped Ge quantum well system, 10 the prevalence of odd minima has gone although the spin-splitting is still the dominant exchange enhanced Zeeman effect.…”

Section: à2mentioning

confidence: 99%

“…The saturation carrier density does not change with wire width due to the low density of surface states at the etched Ge sidewall. 10 The conducting wire width as opposed to the lithographic wire width could not be determined as the low field boundary scattering peak (see Ref. 10) was not well defined.…”

Section: E Narrow Channel Arraysmentioning

confidence: 99%

“…The Hall bar width was 75 lm, considerably larger than the lateral depletion width, determined to be $0.5 6 0.1 lm in narrow wire arrays. 10 Narrow mesas from 3 lm to 1 lm structural width were also fabricated in this undoped material and are discussed in Section III E. Thermally evaporated Al was used as an Ohmic contact and annealed at 250 C for 8 min. The contacts were Ohmic at low temperatures with contact resistance <1.6 kX per contact.…”

Section: A Growth and Processingmentioning

confidence: 99%

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Spin-splitting in p-type Ge devices

Holmes

Newton

Llandro

et al. 2016

Journal of Applied Physics

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Compressively strained Ge quantum well devices have a spin-splitting in applied magnetic field that is entirely consistent with a Zeeman effect in the heavy hole valence band. The spin orientation is determined by the biaxial strain in the quantum well with the relaxed SiGe buffer layers and is quantized in the growth direction perpendicular to the conducting channel. The measured spinsplitting in the resistivity q xx agrees with the predictions of the Zeeman Hamiltonian where the Shubnikov-deHaas effect exhibits a loss of even filling factor minima in the resistivity q xx with hole depletion from a gate field, increasing disorder or increasing temperature. There is no measurable Rashba spin-orbit coupling irrespective of the structural inversion asymmetry of the confining potential in low p-doped or undoped Ge quantum wells from a density of 6 Â 10 10 cm À2 in depletion mode to 1.7 Â 10 11 cm À2 in enhancement. Published by AIP Publishing.

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Engineering the Interfacial Electronic Structure of Epitaxial Ge/AlAs(001) Heterointerfaces via Substitutional Boron Incorporation: The Roles of Doping and Interface Stoichiometry

Clavel

Greene‐Diniz

Grüning

et al. 2019

ACS Appl. Electron. Mater.

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A joint experimental and theoretical framework for the decoupling of boron (B) doping and stoichiometric-induced modifications to the structural properties and electronic band structure of germanium (Ge)/AlAs(001) heterostructures is presented. The effect of B-induced stress on nearest-neighbor Ge bonds is quantified via X-ray diffractometry and Raman spectroscopic analysis and subsequently interpreted through the lens of density functional perturbation theory. Similarly, experimental determination of the energy band alignment at the p-type Ge:B/AlAs heterointerface is understood using a density functional theory approach to model the influence of heterointerface stoichiometry and interatomic bonding between group IV and III–V interfacial atoms on the valence and conduction band discontinuities. The modeled two monolayer interatomic diffusion at the Ge/AlAs heterointerface is confirmed via atom probe tomography analysis, demonstrating a ∼6 Å interfacial width. These results present a unified picture of the Ge:B/AlAs(001) material system, highlighting the influence of B on its structural and electronic properties, and provide a path for the engineering of such heterointerfaces through high concentration dopant incorporation within the overlying Ge epilayer.

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Magnetotransport in p-type Ge quantum well narrow wire arrays

Cited by 6 publications

References 32 publications

Weak localization and weak antilocalization in doped germanium epilayers

Weak localization and weak antilocalization in doped germanium epilayers

Spin-splitting in p-type Ge devices

Engineering the Interfacial Electronic Structure of Epitaxial Ge/AlAs(001) Heterointerfaces via Substitutional Boron Incorporation: The Roles of Doping and Interface Stoichiometry

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