A groundbreaking discovery about wurtzite ferroelectric nitrides is set to revolutionize the landscape of low-power computing, quantum sensing, and high-frequency electronics. These novel semiconductors, capable of maintaining two opposing electrical polarizations within the same material, defied explanation for years due to the puzzling stability of their polarized domains. Researchers at the University of Michigan have now uncovered the atomic-scale mechanism that preserves the integrity of these materials, opening the door to more efficient electronic devices and transformative applications across multiple fields.
Ferroelectric materials possess a unique property akin to magnetism, wherein the alignment of electrical charges within the crystal lattice results in spontaneous polarization. Unlike magnetism, however, these materials bear positive and negative electric poles. Typically, an external electric field can flip the direction of polarization, causing a reversal of charge orientation that remains once the field is removed. Intriguingly, the switching does not usually occur uniformly across the whole material; instead, the semiconductor segregates into distinct regions or domains, each maintaining different orientations of polarization.
Where these electrically charged domains adjoin, especially along boundaries where identical positive poles face one another, conventional wisdom would predict the emergence of severe electrostatic repulsion strong enough to fracture the material. Historically, this contradiction posed a major mystery for materials scientists seeking to understand and harness wurtzite ferroelectric nitrides, thereby limiting their practical utilization. The question of how the crystal lattice maintains stability at these domain walls, despite polarization discontinuities, has been the subject of intense scrutiny.
The University of Michigan team, led by prominent engineers including Zetian Mi and postdoctoral researcher Danhao Wang, applied advanced electron microscopy combined with quantum mechanical modeling to delve into the problem at an atomic resolution. Their analyses revealed a remarkable structural adaptation at the heart of this mystery: the formation of atomic-scale fractures at the interfaces where positive polarizations meet, creating a novel configuration of broken chemical bonds.
These broken bonds play an unexpected yet pivotal role. Rather than introducing detrimental defects, they act as reservoirs of negatively charged dangling electrons. These electrons precisely counterbalance the electrostatic excess positive charge that accumulates at the terminal edges of polarized domains. This elegant self-compensating arrangement prevents the material from pulverizing under internal electric stress, granting it unprecedented stability and robustness.
The theoretical underpinning of this phenomenon reaches further, tracing its origins to the geometry of tetrahedral units that compose the crystal lattice of these semiconductors. According to Emmanouil Kioupakis, a leading materials scientist at the University of Michigan, the unique spatial organization of atoms in these tetrahedra constrains charge distribution in such a way that these stabilizing broken bonds are an inherent, universal feature among tetrahedral ferroelectrics. This insight suggests a broad application of the discovery to a growing class of ferroelectric materials with promising technological prospects.
To validate their findings, the team focused on scandium gallium nitride, a representative wurtzite ferroelectric nitride. High-resolution electron microscopy disclosed that the hexagonal crystal symmetry becomes distorted and buckled across several atomic layers at domain junctions. This local rearrangement shrinks the interlayer spacing and exposes atoms with dangling orbitals—a direct visualization of the theorized broken bonds. Complementary first-principles calculations using density functional theory offered a computational glimpse into the electronic states localized at these fracture lines.
Beyond passive stabilization, the team observed that the dangling electrons form highly conductive pathways along the domain walls, effectively functioning as nanoscale superhighways for electrical current. Remarkably, these channels can support charge carrier densities approximately 100 times greater than those found in conventional gallium nitride transistors. Moreover, the conductivity of these paths is tunable, responding dynamically to changes in the electric field that modulates the polarization domains, allowing for precise control over current flow.
This discovery holds profound implications for microelectronic device design, notably for field-effect transistors (FETs) operating at high frequencies and power levels. The ability to switch these conductive domain interfaces on and off, reposition them within the semiconductor matrix, and tailor their conductivity suggests new architectures that can outperform traditional transistor designs, especially in applications demanding energy-efficient high-speed operation.
The researchers plan to pursue the practical realization of such domain-wall-based transistors, leveraging their unique electrical properties. This next step could inaugurate a new era of electronics where memory, signal processing, and transduction between electrical, optical, and acoustic signals are unified within a single material platform. Such integration promises to minimize power consumption while maximizing device performance.
This breakthrough was achieved through close collaboration between experimentalists and theorists. The electron microscopy work was executed in state-of-the-art nanofabrication and characterization facilities at the University of Michigan, supported by the Lurie Nanofabrication Facility and the Michigan Center for Materials Characterization. Theoretical efforts harnessed supercomputing resources at the National Energy Research Scientific Computing Center, underscoring the interdisciplinary nature of the project.
Co-first authors Danhao Wang, Ding Wang, and Mahlet Molla, along with contributions from colleagues at McGill University, represent the next generation of scientists pushing the boundaries of materials physics and engineering. Their work, funded by the U.S. National Science Foundation, Army Research Office, and the University of Michigan College of Engineering, exemplifies how fundamental science can illuminate pathways to transformative technologies.
In summary, the identification of atomic-scale broken bonds as the key to stabilizing opposing polarizations in wurtzite ferroelectric nitrides is a seminal advancement. It resolves a long-standing enigma and unlocks a functional mechanism to engineer conductive domain walls within semiconductors. This nuanced understanding could catalyze the development of electronic components that are not only smaller and faster but also far more energy-efficient, heralding a significant leap toward sustainable technology.
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Subject of Research: Wurtzite ferroelectric nitrides and domain wall stabilization mechanisms in semiconductors
Article Title: Electric-field-induced domain walls in wurtzite ferroelectrics
Web References:
https://doi.org/10.1038/s41586-025-08812-7
References:
Electric-field-induced domain walls in wurtzite ferroelectrics, Nature, DOI: 10.1038/s41586-025-08812-7
Image Credits: University of Michigan
Keywords
Wurtzite ferroelectric nitrides, semiconductors, electrical polarization, polarization domains, broken bonds, dangling electrons, domain walls, density functional theory, scandium gallium nitride, conductive channels, field effect transistors, microelectronic devices
