Effective g factor of low-density two-dimensional holes in a Ge quantum well

Lu, Tzu-Ming; Harris, Charles Thomas; Huang, S.-H.; Chuang, Yen; Li, J. Y.; Liu, C. W.

doi:10.1063/1.4990569

Cited by 19 publications

(22 citation statements)

References 27 publications

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“…5(d) (right panel), with the range of the g-factor being in good agreement with the fan diagram analysis and other reports in Ge 38 . The observed enhancement of the g-factor with decreasing densities has been previously observed and attributed to an increase in the strength of the effective Coulomb interaction 39,40 or to the non-parabolicity of the valence band 38 .…”

Section: Resultssupporting

confidence: 68%

“…Indeed, gate controlled quantum dots, ballistic 1D channels, and ballistic phase coherent superconductivity were demonstrated recently by using undoped Ge/SiGe. So far the added complexity in developing reliable gate‐stacks has limited the investigation of quantum transport properties in undoped Ge/SiGe to devices with mobilities significantly inferior compared to modulation‐doped structures …”

Section: Introductionmentioning

confidence: 99%

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Shallow and Undoped Germanium Quantum Wells: A Playground for Spin and Hybrid Quantum Technology

Sammak

Sabbagh

Hendrickx

et al. 2019

Adv Funct Materials

127

126

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Buried-channel semiconductor heterostructures are an archetype material platform for the fabrication of gated semiconductor quantum devices. Sharp confinement potential is obtained by positioning the channel near the surface; however, nearby surface states degrade the electrical properties of the starting material. Here, a 2D hole gas of high mobility (5 × 10 5 cm 2 V −1 s −1 ) is demonstrated in a very shallow strained germanium (Ge) channel, which is located only 22 nm below the surface. The top-gate of a dopant-less field effect transistor controls the channel carrier density confined in an undoped Ge/SiGe heterostructure with reduced background contamination, sharp interfaces, and high uniformity. The high mobility leads to mean free paths ≈ 6 µm, setting new benchmarks for holes in shallow field effect transistors. The high mobility, along with a percolation density of 1.2 × 10 11 cm −2 , light effective mass (0.09m e ), and high effective g-factor (up to 9.2) highlight the potential of undoped Ge/SiGe as a low-disorder material platform for hybrid quantum technologies.

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Section: Resultssupporting

confidence: 68%

Section: Introductionmentioning

confidence: 99%

Shallow and Undoped Germanium Quantum Wells: A Playground for Spin and Hybrid Quantum Technology

Sammak

Sabbagh

Hendrickx

et al. 2019

Adv Funct Materials

127

126

View full text Add to dashboard Cite

show abstract

“…The mass is further reduced to 0.035m 0 for device alignment along the <100> direction 166 . Magnetotransport studies 9,167,170 confirmed that 2D holes in strained-Ge exhibit large out-of-plane effective g-factors, with a reported value 170 g * ⊥ ≈20 at a density below 1×10 11 cm −2 . Large spin-splitting energies (up to ≈ 1 meV) were observed 88-90, 139, 159, 161, 162, 164 due to a cubic Rashba-type spin-orbit interaction.…”

Section: Planar Heterostructuresmentioning

confidence: 89%

“…The superior quality achieved in reverse-graded Ge/SiGe heterostructures enabled a plethora of quantum transport studies in modulation-doped etched Hall-bar devices 89,141,[155][156][157][158][159][160][161][162][163][164][165][166][167][168] and, more recently, in undoped H-FETs 45,90,140,154,[169][170][171] . Initial expectations from bandstructure considerations were confirmed and the knowledge-base of confined holes in planar Ge was advanced.…”

Section: Planar Heterostructuresmentioning

confidence: 99%

The germanium quantum information route

et al. 2020

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“…17 The ability to manipulate qubit states by applying microwave electric fields directly to a quantum dot confinement electrode provides the possibility for simplified device layout schemes, in contrast to single-spin electron systems in silicon that have used onchip micromagnets or microwave striplines for qubit control. Further, the large out-of-plane gfactor of up to g ~ 28 in the two-dimensional Ge/SiGe system 22,23 means that a relatively small externally applied magnetic field can be used to set the rotation frequency and facilitate readout in a single spin-based qubit.…”

Section: Introductionmentioning

confidence: 99%

Single and double hole quantum dots in strained Ge/SiGe quantum wells

Hardy

Harris

et al. 2019

Nanotechnology

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Even as today's most prominent spin-based qubit technologies are maturing in terms of capability and sophistication, there is growing interest in exploring alternate material platforms that may provide advantages, such as enhanced qubit control, longer coherence times, and improved extensibility. Recent advances in heterostructure material growth have opened new possibilities for employing hole spins in semiconductors for qubit applications. Undoped, strained Ge/SiGe quantum wells are promising candidate hosts for hole spin-based qubits due to their low disorder, large intrinsic spin-orbit coupling strength, and absence of valley states. Here, we use a simple one-layer gated device structure to demonstrate both a single quantum dot as well as coupling 2 between two adjacent quantum dots. The hole effective mass in these undoped structures, m* ~ 0.08 m0, is significantly lower than for electrons in Si/SiGe, pointing to the possibility of enhanced tunnel couplings in quantum dots and favorable qubit-qubit interactions in an industry-compatible semiconductor platform. CONCLUSIONSWe have demonstrated lithographically defined single and double hole quantum dots in high quality strained Ge/SiGe quantum wells. These results strongly suggest that this material system may serve as a viable host for spin-based qubits (compatible with CMOS processing) and enable quantitative comparisons between quantum dots in electron and hole systems. Multi-metal-layer devices, as are commonly used in Si/SiGe, should be directly applicable to Ge/SiGe to increase the sharpness of tunnel barriers and provide more orthogonal control of coupling between adjacent quantum dots. Development of successful qubit architectures will ultimately call for indepth studies of qubit decoherence mechanisms in this system, in particular the impact of charge noise due to the enhanced spin-orbit coupling. AUTHOR INFORMATION

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Effective g factor of low-density two-dimensional holes in a Ge quantum well

Cited by 19 publications

References 27 publications

Shallow and Undoped Germanium Quantum Wells: A Playground for Spin and Hybrid Quantum Technology

Shallow and Undoped Germanium Quantum Wells: A Playground for Spin and Hybrid Quantum Technology

The germanium quantum information route

Single and double hole quantum dots in strained Ge/SiGe quantum wells

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