Complex quantum transport in a modulation doped strained Ge quantum well heterostructure with a high mobility 2D hole gas

Morrison, C.; Casteleiro, C.; Leadley, D. R.; Myronov, Maksym

doi:10.1063/1.4962432

Cited by 13 publications

(15 citation statements)

References 18 publications

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“…At p = 7.7 × 10 10 cm −2 , ν = 6 at B ∼ 0.53 T is barely resolvable, while ν = 5, 7, and 9 can still be clearly distinguished. This behavior is quite different from what is observed in other Ge 2D hole systems, typically with a much higher hole density [10,19].…”

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confidence: 91%

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

Harris

Huang

et al. 2017

Applied Physics Letters

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confidence: 91%

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

Harris

Huang

et al. 2017

Applied Physics Letters

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“…It is already shown that in p-Si-Ge the device mobility is reduced significantly below that expected for remote ionized impurity-dominated scattering [35][36][37]. However, in strained p-Ge mobilities of approximately 10 6 cm 2 /Vs are possible [38,39] with the same modulation doping and doping offset distance of 20 nm. This reduction in mobility in p-Ge-Sn devices by approximately 10 3 compared to p-Ge and thermal activation is a consequence of the Sn-vacancy hole trap in the Ge cap layer.…”

Section: A Conductance and Mobilitymentioning

confidence: 95%

Activated and Metallic Conduction in p -Type Modulation-Doped Ge - Sn Devices

et al. 2020

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Ge 1−x Sn x quantum wells can be incorporated into Si-Ge-based structures with low-carrier effective masses, high mobilities, and the possibility of direct band-gap devices with x ∼ 0.1. However, the electrical properties of p-type Ge 1−x Sn x devices are dominated by a thermally activated mobility and metallic behavior. At 30 mK the transport measurements indicate localization with a mobility of 380 cm 2 /Vs, which is thermally activated with a temperature-independent carrier density of 4 × 10 11 cm −2. This weakly disordered system with conductivity, σ ∼ e 2 /h, where e is the fundamental charge and h is Planck's constant, is a result of negatively charged "Sn-vacancy" complex states in the barrier layers that act as hole traps. A measured hole effective mass of 0.090 ± 0.005m e from the Shubnikov-de Haas effect, where m e is the free electron mass shows that the valence band is heavy hole dominated and is similar to p-type Ge with the compressive strain playing the role of quenching the spin-orbit coupling and shifting the unoccupied lighthole states to higher hole energies. The Ge 1−x Sn x devices have a high quantum mobility of approximately 36 000 cm 2 /Vs that is not thermally activated. The ratio of transport-to-quantum mobility of approximately 0.01 in Ge 1−x Sn x devices is unusual and points to several competing scattering mechanisms in the different experimental regimes.

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“…Those based on p-type SiGe heterostructures are readily compatible with silicon technology, 24 and, thanks to their intrinsically strong spin-orbit coupling, they are an attractive candidate for the development of topological superconducting systems. 22,[25][26][27][28][29][30][31][32] In this work, we present proof-of-concept S-Sm devices in which the semiconducting element consists of an undoped SiGe heterostucture embedding a strained Ge quantum-well (QW). A high-mobility two-dimensional hole gas (2DHG) is electrostatically accumulated in the QW by means of a surface gate electrode.…”

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Germanium Quantum-Well Josephson Field-Effect Transistors and Interferometers

et al. 2019

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Hybrid superconductor-semiconductor structures attract increasing attention owing to a variety of potential applications in quantum computing devices. They can serve to the realization of topological superconducting systems, as well as gate-tunable superconducting quantum bits. Here we combine a SiGe/Ge/SiGe quantum-well heterostructure hosting high-mobility two-dimensional holes and aluminum superconducting leads to realize prototypical hybrid devices, such as Josephson field-effect transistors (JoFETs) and superconducting quantum interference devices (SQUIDs). We observe gate-controlled supercurrent transport with Ge channels as long as one micrometer and 1 arXiv:1810.05012v2 [cond-mat.mes-hall] 23 Oct 2018 estimate the induced superconducting gap from tunnel spectroscopy measurements in superconducting point-contact devices. Transmission electron microscopy reveals the diffusion of Ge into the aluminum contacts, whereas no aluminum is detected in the Ge channel.Modern quantum nanoelectronics takes increasing advantage of newly synthesized hybrid superconductor-semiconductor (S-Sm) interfaces. 1 One of the main motivations is the search for Majorana zero modes that are predicted to appear in a topological superconductor. 2-4 A Josephson field effect transistor (JoFET) is one of the basic devices. It consists of a gatetunable semiconductor channel allowing Cooper-pair exchange between two superconducting contacts mediated by the superconducting proximity effect. 5 Gate control on the Josephson coupling has eventually led to the realization of electrically tunable transmon quantum bits, now often referred to as gatemons. 6-8 Many of the reported experimental realizations of hybrid S-Sm devices rely on bottomup fabrication starting from semiconductor nanowires or carbon nanotubes. 9-16 Recently, new hybrid S-Sm devices were demonstrated using top-down fabrication processes based on two-dimensional systems made of graphene, 17 InAs, 18,19 GaAs, 20 InGaAs 21 or Ge/SiGe. 22,23Top-down nanoscale devices offer significant advantages in terms of complexity and scalability. Those based on p-type SiGe heterostructures are readily compatible with silicon technology, 24 and, thanks to their intrinsically strong spin-orbit coupling, they are an attractive candidate for the development of topological superconducting systems. 22,[25][26][27][28][29][30][31][32] In this work, we present proof-of-concept S-Sm devices in which the semiconducting element consists of an undoped SiGe heterostucture embedding a strained Ge quantum-well (QW). A high-mobility two-dimensional hole gas (2DHG) is electrostatically accumulated in the QW by means of a surface gate electrode. (Hole mobilities as high as 5×10 5 cm 2 /Vs were reported for similar heterostructures. 12,22,33,34 ) The superconducting proximity effect induces gate-tunable superconductivity in the 2DHG enabling JoFET operation. This functionality is exploited for the realization of gate-controlled superconducting quantum interference

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Complex quantum transport in a modulation doped strained Ge quantum well heterostructure with a high mobility 2D hole gas

Abstract: Maksym. (2016) Complex quantum transport in a modulation doped strained Ge quantum well heterostructure with a high mobility 2D hole gas. Applied Physics Letters, 109 (10). 102103. Permanent WRAP URL:

Cited by 13 publications

References 18 publications

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

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

Activated and Metallic Conduction in p -Type Modulation-Doped Ge - Sn Devices

Germanium Quantum-Well Josephson Field-Effect Transistors and Interferometers

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