From left to right, graduate students Yutong Guo and Anindita Chakravarty work
in the lab of Huamin Li, assistant professor of electrical engineering. Courtesy:
Douglas Levere, University at Buffalo.
University
at Buffalo researchers are reporting a new, two-dimensional transistor made of
graphene and the compound molybdenum disulfide that could help usher in a new
era of computing.
As
described in a paper accepted at the 2020 IEEE International Electron Devices
Meeting, which is taking place virtually next week, the transistor requires
half the voltage of current semiconductors. It also has a current density
greater than similar transistors under development.
This
ability to operate with less voltage and handle more current is key to meet the
demand for new power-hungry nanoelectronic devices, including quantum
computers.
"New
technologies are needed to extend the performance of electronic systems in
terms of power, speed, and density. This next-generation transistor can rapidly
switch while consuming low amounts of energy," says the paper's lead
author, Huamin Li, Ph.D., assistant professor of electrical engineering in the
UB School of Engineering and Applied Sciences (SEAS).
The transistor is composed of a single layer of graphene and a single layer of molybdenum disulfide, or MoS2, which is a part of a group of compounds known as transition metals chalcogenides. The graphene and MoS2 are stacked together, and the overall thickness of the device is roughly 1 nanometer—for comparison, a sheet of paper is about 100,000 nanometers.
An
illustration of the transistor showing graphene (black hexagons) and molybdenum
disulfide (blue and yellow layered structure) among other components. Credit:
University at Buffalo.
Courtesy: University at Buffalo.
While most
transistors require 60 millivolts for a decade of change in current, this new
device operates at 29 millivolts.
It's able
to do this because the unique physical properties of graphene keep electrons
"cold" as they are injected from the graphene into the MoS2 channel.
This process is called Dirac-source injection. The electrons are considered
"cold" because they require much less voltage input and, thus,
reduced power consumption to operate the transistor.
An even
more important characteristic of the transistor, Li says, is its ability to
handle a greater current density compared to conventional transistor
technologies based on 2-D or 3-D channel materials. As described in the study,
the transistor can handle 4 microamps per micrometer.
"The
transistor illustrates the enormous potential 2-D semiconductors and their
ability to usher in energy-efficient nanoelectronic devices. This could
ultimately lead to advancements in quantum research and development, and help
extend Moore's Law," says co-lead author Fei Yao, Ph.D., assistant
professor in the Department of Materials Design and Innovation, a joint program
of SEAS and UB's College of Arts of Sciences.