我们进行详细的磁输运的二维电子气（2DEG）在未掺杂的Si/SiGe异质结构中形成的研究，以确定在这个日益重要的材料系统中的电子迁移率限制机制。通过分析来自26个具有不同异质结生长轮廓的晶片的数据，我们观察到Si量子阱中的背景氧浓度与最大迁移率之间的强相关性。最高质量的晶片支持2DEG，其迁移率为160，000 cm^2/Vs，密度为2.17 x 10^11/cm^2，并在临界密度为0.46 x 10^11/cm^2时表现出金属到绝缘体的转变。在1.8 T的磁场下，我们提取了约150微eV的谷分裂。这些结果表明，未掺杂的Si/SiGe异质结构适合于制备少电子量子点。
英文摘要：
We perform detailed magnetotransport studies on two-dimensional electron gases (2DEGs) formed in undoped Si/SiGe heterostructures in order to identify the electron mobility limiting mechanisms in this increasingly important materials system. By analyzing data from 26 wafers with different heterostructure growth profiles we observe a strong correlation between the background oxygen concentration in the Si quantum well and the maximum mobility. The highest quality wafer supports a 2DEG with a mobility of 160,000 cm^2/Vs at a density 2.17 x 10^11/cm^2 and exhibits a metal-to-insulator transition at a critical density 0.46 x 10^11/cm^2. We extract a valley splitting of approximately 150 microeV at a magnetic field of 1.8 T. These results provide evidence that undoped Si/SiGe heterostructures are suitable for the fabrication of few-electron quantum dots.
We report density-dependent effective hole mass measurements in undoped germanium quantum wells. We are able to span a large range of densities ($2.0-11\times10^{11}$ cm$^{-2}$) in top-gated field effect transistors by positioning the strained buried Ge channel at different depths of 12 and 44 nm from the surface. From the thermal damping of the amplitude of Shubnikov-de Haas oscillations, we measure a light mass of $0.061m_e$ at a density of $2.2\times10^{11}$ cm$^{-2}$. We confirm the theoretically predicted dependence of increasing mass with density and by extrapolation we find an effective…
We report low-temperature magneto-transport measurements of an undoped Si/SiGe asymmetric double quantum well heterostructure. The density in both layers is tuned independently utilizing a top and a bottom gate, allowing the investigation of quantum wells at both imbalanced and matched densities. Integer quantum Hall states at total filling factor $ν_{\text{T}} = 1$ and $ν_{\text{T}} = 2$ are observed in both density regimes, and the evolution of their excitation gaps is reported as a function of density. The $ν_{\text{T}} = 1$ gap evolution departs from the behavior generally observed for val…
Optically programmable and erasable cryogenic flash memory on an undoped Si/SiGe heterostructure
Center for Research in Nanotechnology and Science, Indian Institute of Technology Bombay（印度孟买理工学院纳米科学与技术研究中心）；Department of Physics, Indian Institute of Technology Bombay（印度孟买理工学院物理系）；QuTech and Kavli Institute of Nanoscience, Delft University of Technology（代尔夫特理工大学QuTech和卡弗里纳米科学研究所）；Centre of Excellence in Quantum Information, Computing, Science & Technology, IIT Bombay（印度孟买理工学院量子信息、计算、科学与技术卓越中心）
Low-Noise Quantum Dots in Ultra-Shallow Ge/SiGe Heterostructures for Prototyping Hybrid Semiconducting-Superconducting Devices
Institute of Science and Technology Austria（奥地利科学与技术研究所）；Catalan Institute of Nanoscience and Nanotechnology – ICN2 (CSIC and BIST)（加泰罗尼亚纳米科学技术研究所（CSIC和BIST））
Valley physics in the two bands $\mathbf{k}\cdot\mathbf{p}$ model for SiGe heterostructures and spin qubits
Univ. Grenoble Alpes, CEA, Leti（格勒诺布尔大学，CEA，LETI）；Institute of Theoretical Physics, University of Regensburg（雷根斯堡大学理论物理研究所）；Univ. Grenoble Alpes, CEA, IRIG-MEM-L_Sim（格勒诺布尔大学，CEA，IRIG-MEM-L_Sim）
Electron transport through antidot superlattices in $Si/SiGe$ heterostructures: new magnetoresistance resonances in lattices with large diameter antidots
Reducing disorder in Ge quantum wells by using thick SiGe barriers
Delft University of Technology（代尔夫特理工大学）；University of Maryland, College Park（马里兰大学帕克分校）；Catalan Institute of Nanoscience and Nanotechnology (ICN2)（加泰罗尼亚纳米科学和纳米技术研究所）
We show that Ge concentration oscillations within the quantum well region of a Si/SiGe heterostructure can significantly enhance the spin-orbit coupling of the low-energy conduction-band valleys. Specifically, we find that for Ge oscillation wavelengths near $λ= 1.57~\text{nm}$ with an average Ge concentration of $\bar{n}_{\text{Ge}} = 5\%$ in the quantum well region, a Dresselhaus spin-orbit coupling is induced, at all physically relevant electric field strengths, which is over an order of magnitude larger than what is found in conventional Si/SiGe heterostructures without Ge concentration os…
Cryogenic interface-state filling and tunneling mechanisms in strained Ge/SiGe heterostructures
University of Science and Technology of China（中国科学技术大学）；CAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China（中国科学院量子信息与量子物理学前沿卓越中心）；Hefei National Laboratory（合肥国家实验室）；Beijing Superstring Academy of Memory Technology（北京超弦记忆技术研究院）；Origin Quantum Computing Company Limited（本源量子计算科技有限责任公司）
The valley degree of freedom presents challenges and opportunities for silicon spin qubits. An important consideration for singlet-triplet states is the presence of two distinct triplets, comprised of valley vs. orbital excitations. Here we show that both of these triplets are present in the typical operating regime, but that only the valley-excited triplet offers intrinsic protection against charge noise. We further show that this protection arises naturally in dots with stronger confinement. These results reveal an inherent advantage for silicon-based multi-electron qubits.
Simultaneous study of acoustic and optic phonon scattering of electrons and holes in undoped $\mathrm{GaAs}$/$\mathrm{Al_{x} Ga_{1-x} As}$ heterostructures
本研究利用非掺杂 GaAs/AlGaAs 异质结构，通过电阻率温度依赖性测量，在 1.6-92.5K 范围内同步研究了二维电子和空穴的声学与光学声子散射，提取了耦合常数和 LO 激活能，验证了该方法的有效性。
Valley splitting of Si/SiGe heterostructures in tilted magnetic fields
本文研究了高质量Si/Si $_{1-x}$ Ge $_x$异质结构中二维电子在倾斜磁场作用下的谷分裂。对于我们研究中的所有样品，填充因子$ν=3$（$Δ_3$）处的谷分裂在符合角之前和之后显著不同，在符合角处能级在费米能级处交叉。在重合的两侧，观察到$Δ_3$对电子密度的线性密度依赖性，而这两种配置的斜率相差超过两倍。我们认为，屏蔽的库仑相互作用从低洼的填充水平，这也解释了所观察到的自旋相关的电阻率，是负责的大差异$Δ_3$之前和之后的重合。
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 cou…
Increasing valley splitting in Si/SiGe by practically achievable heterostructure profiles
Fakultät für Physik, Universität Regensburg（雷根斯堡大学物理学院）；ResQ Resonant Quantum Systems FlexCo（ResQ共振量子系统FlexCo公司）；RIKEN, Center for Quantum Computing (RQC)（理化学研究所量子计算中心）；Institute of Physics, Slovak Academy of Sciences（斯洛伐克科学院物理研究所）；Univ. Grenoble Alpes, CEA, IRIG-MEM-L Sim（格勒诺布尔阿尔卑斯大学法国原子能和替代能源委员会研究信息部模拟实验室）；Physics Department, King Fahd University of Petroleum and Minerals（法赫德国王石油矿产大学物理系）；Center for Advanced Quantum Computing, KFUPM（法赫德国王石油矿产大学先进量子计算中心）；Department of Physics, University of Basel（巴塞尔大学物理系）
Donor states in modulation-doped Si/SiGe heterostructures
提出了一种计算异质结构量子阱内外浅施主性质的统一方法。该方法不仅可以得到任意对称性的所有局域态的结合能，而且可以得到局域态随连续量子阱子带简并时可能出现的共振态的能量宽度。该方法是非变分的，因此我们也能够评估的波函数。这用于计算光学吸收光谱，由于选择规则，该光谱是强非各向同性的。从Si/Si $_{1-x}$ Ge $_x$量子阱的计算结果，使我们能够提出的杂质态的一般行为，作为施主的位置是不同的从中心的井内的势垒深处。同时考虑了中心晶胞效应和晶格失配引起的应变对施主基态的影响。
Electron transport in Si/SiGe modulation-doped heterostructures using Monte Carlo simulation
用蒙特卡罗模拟研究了拉伸应变Si 1-xGex/Si/Si 1-xGex异质结构中二维气体的电子输运.首先研究了非栅调制掺杂结构中的电子迁移率。在较宽的电子密度范围内，计算结果与实验结果吻合得很好.迁移率通常在高掺杂结构中的1100 cm 2/Vs和低电子密度下的2800 cm 2/Vs之间变化。的迁移率被证明是显着影响的间隔层的厚度分离的应变Si沟道的脉冲掺杂的供应层。在此基础上，研究了寄生路径贡献可以忽略的栅控调制掺杂结构中的电子输运。的迁移率被证明是高于可比ungated结构和依赖于栅极电压，作为远程杂质屏蔽的电子密度依赖的结果。
Low-loss frequency-tunable Josephson junction array cavities on Ge/SiGe heterostructures with a tapered etching approach
École Polytechnique Fédérale de Lausanne (EPFL)（洛桑联邦理工学院）；Hybrid Quantum Circuits Laboratory（混合量子电路实验室）；Institute of Physics, École Polytechnique Fédérale de Lausanne (EPFL)（洛桑联邦理工学院物理研究所）；Center for Quantum Science and Engineering, École Polytéchnique Fédérale de Lausanne (EPFL)（洛桑联邦理工学院量子科学与工程中心）
Two-dimensional electron gas (2DEG) in interfaces and surfaces based on perovskite SrTiO$_3$ (STO) has exhibited various interesting phenomena and is used to develop oxide electronics. Recently, KTaO$_3$ (KTO) shows great potential and is believed to host more exciting effects and phenomena toward novel devices. Here, through first-principles investigation and analysis, we find two types of coexisting 2DEG and 2D hole gas (2DHG) highly confined at the interfaces in undoped STO/KTO/BaTiO$_3$ heterostructures, when the KTO thickness $m$ reaches a crititcal value. The two interfaces are made by (…
Silicon-germanium heterostructures have successfully hosted quantum dot qubits, but the intrinsic near-degeneracy of the two lowest valley states poses an obstacle to high fidelity quantum computing. We present a modification to the Si/SiGe heterostructure by the inclusion of a spike in germanium concentration within the quantum well in order to increase the valley splitting. The heterostructure is grown by chemical vapor deposition and magnetospectroscopy is performed on gate-defined quantum dots to measure the excited state spectrum. We demonstrate a large and widely tunable valley splitting…
Optimization of Si/SiGe Heterostructures for Large and Robust Valley Splitting in Silicon Qubits
Weierstrass Institute for Applied Analysis and Stochastics (WIAS)（魏茨塞克应用分析与随机过程研究所）；RWTH Aachen University（亚琛工业大学）；Forschungszentrum Jülich（于利希研究中心）；Institute of Quantum Information（量子信息研究所）；ARQUE Systems GmbH（ARQUE系统有限公司）
Enhancing valley splitting in SiGe heterostructures is a crucial task for developing silicon spin qubits. Complex SiGe heterostructures, sharing a common feature of four-monolayer (4ML) Ge layer next to the silicon quantum well (QW), have been computationally designed to have giant valley splitting approaching 9 meV. However, none of them has been fabricated may due to their complexity. Here, we remarkably simplify the original designed complex SiGe heterostructures by laying out the Si QW directly on the Ge substrate followed by capping a (Ge4Si4)n superlattice(SL) barrier with a small sacrif…
