Electronic-band parameters in strained<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Si</mml:mi></mml:mrow><mml:mrow><mml:mn>1</mml:mn><mml:mi mathvariant="normal">−</mml:mi><mml:mi mathvariant="italic">x</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Ge</mml:mi></mml:mrow><mml:mrow><mm

Rieger, Martin; Vogl, P.

doi:10.1103/physrevb.48.14276

Cited by 586 publications

(245 citation statements)

References 51 publications

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“…The theory of the variation of E (∆) with x is not germane to the present work, and we simply quote the empirical result, linear in x, which is consistent with Ref. 18 :…”

Section: The Strained Silicon Quantum Wellsupporting

confidence: 82%

Decoherence of electron spin qubits in Si-based quantum computers

2002

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Direct phonon spin-lattice relaxation of an electron qubit bound by a donor impurity or quantum dot in SiGe heterostructures is investigated. The aim is to evaluate the importance of decoherence from this mechanism in several important solid-state quantum computer designs operating at low temperatures. We calculate the relaxation rate 1/T1 as a function of [100] uniaxial strain, temperature, magnetic field, and silicon/germanium content for Si:P bound electrons. The quantum dot potential is much smoother, leading to smaller splittings of the valley degeneracies. We have estimated these splittings in order to obtain upper bounds for the relaxation rate. In general, we find that the relaxation rate is strongly decreased by uniaxial compressive strain in a SiGe-Si-SiGe quantum well, making this strain an important positive design feature. Ge in high concentrations (particularly over 85%) increases the rate, making Si-rich materials preferable. We conclude that SiGe bound electron qubits must meet certain conditions to minimize decoherence but that spin-phonon relaxation does not rule out the solid-state implementation of error-tolerant quantum computing.

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“…The theory of the variation of E (∆) with x is not germane to the present work, and we simply quote the empirical result, linear in x, which is consistent with Ref. 18 :…”

Section: The Strained Silicon Quantum Wellsupporting

confidence: 82%

Decoherence of electron spin qubits in Si-based quantum computers

2002

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“…The two-dimensional electron gas is defined in the thin silicon layer with tensile strain. 38,87 The in-plane effective mass is isotropic, given by the transverse mass of the X valley states, 41 and we use m = 0.198m e , 88 where m e is the free-electron mass. The effective Landé factor is g = 2.…”

Section: Modelmentioning

confidence: 99%

Theory of spin relaxation in two-electron laterally coupled Si/SiGe quantum dots

2012

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Highly accurate numerical results of phonon-induced two-electron spin relaxation in silicon double quantum dots are presented. The relaxation, enabled by spin-orbit coupling and the nuclei of 29 Si (natural or purified abundance), is investigated for experimentally relevant parameters, the interdot coupling, the magnetic field magnitude and orientation, and the detuning. We calculate relaxation rates for zero and finite temperatures (100 mK), concluding that our findings for zero temperature remain qualitatively valid also for 100 mK. We confirm the same anisotropic switch of the axis of prolonged spin lifetime with varying detuning as recently predicted in GaAs. Conditions for possibly hyperfine-dominated relaxation are much more stringent in Si than in GaAs. For experimentally relevant regimes, the spin-orbit coupling, although weak, is the dominant contribution, yielding anisotropic relaxation rates of at least two orders of magnitude lower than in GaAs.

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“…For the n-type Si-rich systems, we simulated pure Si wells with 22% Ge barriers. As SiGe alloys are type-II semiconductors, [16] the well and barrier materials were swapped over for the p-type structure. For the Ge-rich system, pure Ge wells with 22% Si barriers were used.…”

Section: Diffuse Bandstructurementioning

confidence: 99%

“…[16] In (001) oriented heterostructures, strain breaks the valley degeneracy and the conduction band edge lies in the two ∆ z valleys (with their major axes in reciprocal space aligned with the growth direction). [13] The quantisation effective mass of these valleys is m q = 0.916.…”

Section: N-type (001) Oriented Si-rich Structuresmentioning

confidence: 99%

Growth variation effects in SiGe-based quantum cascade lasers

Valavanis¹,

Ikonić²,

Kelsall³

2009

J. Opt. A: Pure Appl. Opt.

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Abstract. Epitaxial growth of SiGe quantum cascade (QC) lasers has thus far proved difficult, and nonabrupt Ge profiles are known to exist. We model the resulting barrier degradation by simulating annealing in pairs of quantum wells (QWs). Using a semiclassical charge transport model, we calculate the changes in scattering rates and transition energy between the lowest pair of subbands.We compare results for each of the possible material configurations for SiGe QC lasers. The effects are most severe in n-type (001) Si-rich systems due to the large effective electron mass, and in p-type systems due to the coexistence of light-and heavy-holes.The lower effective mass and conduction band offset of (111) oriented systems minimises transition energy variation, and a large interdiffusion length (L d = 1.49 nm) is tolerated with respect to scattering rate. Ge-rich systems are shown to give the best tolerance with respect to subband separation (L d = 3.31 nm), due also to their low effective mass.

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Electronic-band parameters in strainedSi1−xGe

Cited by 586 publications

References 51 publications

Decoherence of electron spin qubits in Si-based quantum computers

Decoherence of electron spin qubits in Si-based quantum computers

Theory of spin relaxation in two-electron laterally coupled Si/SiGe quantum dots

Growth variation effects in SiGe-based quantum cascade lasers

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