Enhancement-mode buried strained silicon channel quantum dot with tunable lateral geometry

Abstract

We propose and demonstrate a relaxed-SiGe/strained-Si (SiGe/s-Si) enhancement-mode gate stack for quantum dots. The enhancement-mode SiGe/s-Si structure is pursued because it spaces the quantum dot away from charge and spin defect rich dielectric interfaces and minimizes background dopants. A mobility of 1.6 × 10 5 cm 2 /Vs at 5.8 × 10 11 /cm 2 is measured in Hall bars that witness the same device process flow as the quantum dot. Periodic Coulomb blockade (CB) is measured in a double-top-gated lateral quantum dot nanostructure. The CB terminates with open diamonds up to ±10 mV of DC voltage across the device. The devices were fabricated within a 150 mm Si foundry setting that uses implanted ohmics and chemical-vapor-deposited dielectrics, in contrast to previously demonstrated enhancement-mode SiGe/s-Si structures made with AuSb alloyed ohmics and atomic-layer-deposited dielectric. A modified implant, polysilicon formation and annealing conditions were utilized to minimize the thermal budget so that the buried s-Si layer would not be washed out by Ge/Si interdiffusion.

Nuclear spin induced decoherence of a quantum dot in Si confined at a SiGe interface: Decoherence dependence on73Ge

“…(1) is due to a variable vertical E field F z , which simulates the effect of a top enhancement gate. 9 A harmonic potential represents a reasonably good estimate of the confinement for electrostatically gated structures. 10 While minor numerical variations of the results presented here are expected for much smaller dot sizes, in which the local alloy disorder has greater impact from sample to sample, the same trends and order of magnitude estimates will remain valid.…”

Coherent electrical rotations of valley states in Si quantum dots using the phase of the valley-orbit coupling

“…Reliable numbers for 1/f noise in single and double Si QDs are scarce, though 1/f noise and the charge offset drift has been measured in SETs 96 and are indicative of the results to be expected in QDs. At the same time, there has been progress of late in combating the effect of noise in QD spin qubits, such as a singlet-triplet qubit via dynamical decoupling, 97 composite pulses, 98 and by growing a buried quantum dot 99 further from the interface.…”

Scattering mechanisms in shallow undoped Si/SiGe quantum wells

“…7 This massive mobility increase opens up the possibility to fabricate and improve upon Si/SiGe nano-devices such as quantum wires 8,9 and quantum dots. [10][11][12][13] When patterning nano-structures, a balance must be attained between high mobility, usually achieved in channels buried deep underneath the surface (∼ 500 nm), and a sharp confinement potential, which is sharper the shallower the channel is. Sharp confinement allows for fabrication of smaller and better defined nano-structures.…”