Integrating Si/SiGe quantum devices with on-chip classical circuitry
Explore the source record for details and available documents.
Campbell, DeAnna Marie↗
Engineering topics
Tracy, Lisa A.
Publications and source records attributed to Tracy, Lisa A..
Low thermal budget high-k/metal surface gate for buried donor-based devices
Not Available
36 MATERIALS SCIENCE↗
Artificial Graphene in Undoped Semiconductor Heterostructures
The linear energy-momentum dispersion which arises from graphene’s underlying honeycomb lattice gives graphene its unique electronic properties unfound in conventional semiconductors. Theoretically speaking, when an electrostatic potential with hexagonal or honeycomb symmetry is imposed onto a two-dimensional electron/hole system, the band structure is modified in a way that the same linear energy-momentum dispersion could exist. Experimentally, there has not been any evidence from transport demonstrating the so-called “artificial graphene”. In this project, we attempt to create an artificial superlattice potential with hexagonal symmetry for two dimensional carriers in an undoped SiGe heterostructure by patterning a nanoscale hole array in a metallic gate. Using undoped heterostructures allows us to access a very wide density range, which covers the magic densities at which the Dirac points are expected. A process flow for fabricating such field-effect-transistor devices with a lattice constant as small as 90 nm is reported. Magneto-transport measurements performed at 0.3 K show that the superlattice potential in the quantum well in which the two-dimensional system resides is indeed modulated by the gates. However, no signature of the sought-after linear dispersion is observed in the transport data.
36 MATERIALS SCIENCE↗
Designer quantum materials
Quantum materials have long promised to revolutionize everything from energy transmission (high temperature superconductors) to both quantum and classical information systems (topological materials). However, their discovery and application has proceeded in an Edisonian fashion due to both an incomplete theoretical understanding and the difficulty of growing and purifying new materials. This project leverages Sandia's unique atomic precision advanced manufacturing (APAM) capability to design small-scale tunable arrays (designer materials) made of donors in silicon. Their low-energy electronic behavior can mimic quantum materials, and can be tuned by changing the fabrication parameters for the array, thereby enabling the discovery of materials systems which can't yet be synthesized. In this report, we detail three key advances we have made towards development of designer quantum materials. First are advances both in APAM technique and underlying mechanisms required to realize high-yielding donor arrays. Second is the first-ever observation of distinct phases in this material system, manifest in disordered 2D sheets of donors. Finally are advances in modeling the electronic structure of donor clusters and regular structures incorporating them, critical to understanding whether an array is expected to show interesting physics. Combined, these establish the baseline knowledge required to manifest the strongly-correlated phases of the Mott-Hubbard model in donor arrays, the first step to deploying APAM donor arrays as analogues of quantum materials.
36 MATERIALS SCIENCE↗