A new class of chips, ferroelectric semiconductors, can store information in an electric field, allowing for low power computers, quantum-precision sensors, and the conversion of signals between electrical, optical and acoustic forms.
However, chips tend to collapse under these conditions, and the way ferroelectric semiconductors maintain two opposite electrical polarizations in the same material has previously remained a mystery.
A team led by University of Michigan engineers has discovered why a material called Wurtzite Ferroelectric Nitrides doesn’t tear itself.
Zetian MI, Pallab K. Bhattacharya, author of Collegiate Engineering and Co-compon-componseding, explained:
“However, the underlying mechanisms for ferroelectric switching and charge compensation remain elusive. How stable is the material? It was largely unknown.”
Polarization changes in ferroelectric semiconductors
In many cases, it is not the entire material that switches polarization. Instead, it is divided into original polarized and inverse polarized domains.
Where these domains meet, especially when the two positive objectives come together, the researchers did not understand why repulsion did not give the ferroelectric semiconductor a physical break.
“As a rule, polarization discontinuities are not stable,” said Dan Hao Wang, a postdoctoral researcher in electrical and computer engineering and a co-author of the study.
“These interfaces have unique atomic arrangements that have never been observed before. What’s even more exciting is that we’ve observed that this structure may be suitable for future transistor conductive channels.”
Adhesives that hold bonds together
Experimental studies have revealed that the team has an atomic scale rest in the material. But that break creates the glue that brings it together.
The horizontal joints where the two positive ends meet, with the crystal structure being broken and there are many hanging bonds.
These bonds contain negatively charged electrons that perfectly balance the excess positive charge at the ends of each domain in the ferroelectric semiconductor.
Commented by Emmaniul Kiopakis, professor of material science and engineering and corresponding author, “We are a great source of knowledge and knowledge. “It’s a simple and elegant result. Abrupt polarization changes usually cause harmful defects, but in this case the resulting broken bond provides precisely the charge required to stabilize the material.”
“This makes it a universal stabilization mechanism in all ferroelectrics, a class of materials that is rapidly gaining attention for their potential in next-generation microelectronic devices.”
Gallium nitride supports high flow
With electron microscopes, the team discovered that the atomic structure of the ferroelectric semiconductor is made up of scandium nitride.
When the domains met, the normal hexagonal crystal structures sat in several atomic layers, creating broken bonds. Microscopy showed that the layers were closer than usual, but that calculations of the functional theory of density is required to reveal the dangling bond structure.
In addition to holding the material together, the electrons in the dangling coupling create an adjustable superhighway for electrical along the joint, with approximately 100 times more charge carriers than regular nitride transistors.
That highway can be more or less conductive by turning off, moving within the material and reversing, moving, strengthening or weakening the electric field that sets the polarization.
The team quickly realised its potential as a field effect transistor that supports high currents and is suitable for high power and high frequency electronics. This is the plan they will build next.
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