A quantum dot crossbar with sublinear scaling of interconnects at cryogenic temperature

We demonstrate a 36 × 36 gate electrode crossbar that supports 648 narrow-channel field effect transistors (FET) for gate-defined quantum dots, with a quadratic increase in quantum dot count upon a linear increase in control lines. The crossbar is fabricated on an industrial ²⁸Si-MOS stack and shows 100% FET yield at cryogenic...

Qubits made by advanced semiconductor manufacturing

Full-scale quantum computers require the integration of millions of qubits, and the potential of using industrial semiconductor manufacturing to meet this need has driven the development of quantum computing in silicon quantum dots. However, fabrication has so far relied on electron-beam lithography and, with a few exceptions, conventional...

Lightly strained germanium quantum wells with hole mobility exceeding one million

We demonstrate that a lightly strained germanium channel (ϵ / / = - 0.41 %) in an undoped Ge/Si0.1Ge0.9 heterostructure field effect transistor supports a two-dimensional (2D) hole gas with mobility in excess of 1 × 10 6 cm2/Vs and percolation density less than 5 × 10 10 cm-2. This low disorder 2D hole system shows tunable fractional quantum...

Atomic fluctuations lifting the energy degeneracy in Si/SiGe quantum dots

Electron spins in Si/SiGe quantum wells suffer from nearly degenerate conduction band valleys, which compete with the spin degree of freedom in the formation of qubits. Despite attempts to enhance the valley energy splitting deterministically, by engineering a sharp interface, valley splitting fluctuations remain a serious problem for qubit...

Valley Splitting in Silicon from the Interference Pattern of Quantum Oscillations

We determine the energy splitting of the conduction-band valleys in two-dimensional electrons confined in silicon metal oxide semiconductor Hall-bar transistors. These silicon metal oxide semiconductor Hall bars are made by advanced semiconductor manufacturing on 300 mm silicon wafers and support a two-dimensional electron gas of high quality...

Wafer-scale low-disorder 2DEG in ²⁸Si/SiGe without an epitaxial Si cap

We grow 28Si/SiGe heterostructures by reduced-pressure chemical vapor deposition and terminate the stack without an epitaxial Si cap but with an amorphous Si-rich layer obtained by exposing the SiGe barrier to dichlorosilane at 500 °C. As a result, 28Si/SiGe heterostructure field-effect transistors feature a sharp semiconductor/dielectric...

Low percolation density and charge noise with holes in germanium

We engineer planar Ge/SiGe heterostructures for low disorder and quiet hole quantum dot operation by positioning the strained Ge channel 55 nm below the semiconductor/dielectric interface. In heterostructure field effect transistors, we measure a percolation density for two-dimensional hole transport of 2.1 × 10 10 cm−2 , indicative of a very...

Engineering of the spin on dopant process on silicon on insulator substrate

We report on a systematic analysis of phosphorus diffusion in silicon on insulator thin film via spin-on-dopant process (SOD). This method is used to provide an impurity source for semiconductor junction fabrication. The dopant is first spread into the substrate via SOD and then diffused by a rapid thermal annealing process. The dopant...

InSbAs Two-Dimensional Electron Gases as a Platform for Topological Superconductivity

Topological superconductivity can be engineered in semiconductors with strong spin-orbit interaction coupled to a superconductor. Experimental advances in this field have often been triggered by the development of new hybrid material systems. Among these, two-dimensional electron gases (2DEGs) are of particular interest due to their inherent...

Quantum dot arrays in silicon and germanium

Electrons and holes confined in quantum dots define excellent building blocks for quantum emergence, simulation, and computation. Silicon and germanium are compatible with standard semiconductor manufacturing and contain stable isotopes with zero nuclear spin, thereby serving as excellent hosts for spins with long quantum coherence. Here, we...

Effect of Quantum Hall Edge Strips on Valley Splitting in Silicon Quantum Wells

We determine the energy splitting of the conduction-band valleys in two-dimensional electrons confined to low-disorder Si quantum wells. We probe the valley splitting dependence on both perpendicular magnetic field B and Hall density by performing activation energy measurements in the quantum Hall regime over a large range of filling factors....

Vanishing Zeeman energy in a two-dimensional hole gas

A clear signature of Zeeman split states crossing is observed in a Landau fan diagram of strained germanium two-dimensional hole gas. The underlying mechanisms are discussed based on a perturbative model yielding a closed formula for the critical magnetic fields. These fields depend strongly on the energy difference between the topmost and...

Plasmon-enhanced Ge-based metal-semiconductor-metal photodetector at near-IR wavelengths

We demonstrate the use of plasmonic effects to boost the near-infrared sensitivity of metal-semiconductor-metal detectors. Plasmon-enhanced photodetection is achieved by properly optimizing Au interdigitated electrodes, micro-fabricated on Ge, a semiconductor that features a strong near IR absorption. Finite-difference time-domain simulations...

Light effective hole mass in undoped Ge/SiGe quantum wells

We report density-dependent effective hole mass measurements in undoped germanium quantum wells. We are able to span a large range of densities (2.0-11×1011cm-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...

Ballistic superconductivity and tunable pi-junctions in InSb quantum wells

Planar Josephson junctions (JJs) made in semiconductor quantum wells with large spin-orbit coupling are capable of hosting topological superconductivity. Indium antimonide (InSb) two-dimensional electron gases (2DEGs) are particularly suited for this due to their large Landé g-factor and high carrier mobility, however superconducting hybrids...

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

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...