A Noninvasive Method for Nanoscale Electrostatic Gating of Pristine Materials

Electrostatic gating is essential
for defining and control of semiconducting devices. However, nanofabrication
processes required for depositing gates inevitably degrade the pristine
quality of the material of interest. Examples of materials that suffer
from such degradation include ultrahigh mobility GaAs/AlGaAs two-dimensional
electron gases (2DEGs), graphene, topological insulators, and nanowires.
To preserve the pristine material properties, we have developed a
flip-chip setup where gates are separated from the material by a vacuum,
which allows nanoscale electrostatic gating of the material without
exposing it to invasive nanoprocessing. An additional benefit is the
vacuum between gates and material, which, unlike gate dielectrics,
is free from charge traps. We demonstrate the operation and feasibility
of the flip-chip setup by achieving quantum interference at integer
quantum Hall states in a Fabry–Pérot interferometer
based on a GaAs/AlGaAs 2DEG. Our results pave the way for the study
of exotic phenomena including fragile fractional quantum Hall states
by preserving the high quality of the material.