Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


The culprit of some GaN defects could be nitrogen


Using molecular dynamics, researchers demonstrate the possible role of nitrogen as a major contributor to dislocation-related effects in gallium nitride-based devices.

As silicon-based semiconductors reach their performance limits, gallium nitride (GaN) is becoming the next go-to material to advance light-emitting diode (LED) technologies, high-frequency transistors and photovoltaic devices. Holding GaN back, however, is its high numbers of defects.

As silicon-based semiconductors reach performance limits, gallium nitride is becoming the next go-to material for several technologies. Holding GaN back, however, is its high numbers of defects. Better understanding how GaN defects form at the atomic level could improve the performance of the devices made using this material. Researchers have taken a significant step by examining and determining six core configurations of the GaN lattice. They present their findings in the Journal of Applied Physics. This image shoes the distribution of stresses per atom (a) and (b) of a-edge dislocations along the <1-100> direction in wurtzite GaN.

Credit: Physics Department, Aristotle University of Thessaloniki

This material degradation is due to dislocations -- when atoms become displaced in the crystal lattice structure. When multiple dislocations simultaneously move from shear force, bonds along the lattice planes stretch and eventually break. As the atoms rearrange themselves to reform their bonds, some planes stay intact while others become permanently deformed, with only half planes in place. If the shear force is great enough, the dislocation will end up along the edge of the material.

Layering GaN on substrates of different materials makes the problem that much worse because the lattice structures typically don't align. This is why expanding our understanding of how GaN defects form at the atomic level could improve the performance of the devices made using this material.

A team of researchers has taken a significant step toward this goal by examining and determining six core configurations of the GaN lattice. They presented their findings in the Journal of Applied Physics, from AIP Publishing.

"The goal is to identify, process and characterize these dislocations to fully understand the impact of defects in GaN so we can find specific ways to optimize this material," said Joseph Kioseoglou, a researcher at the Aristotle University of Thessaloniki and an author of the paper.

There are also problems that are intrinsic to the properties of GaN that result in unwanted effects like color shifts in the emission of GaN-based LEDs. According to Kioseoglou, this could potentially could be addressed by exploiting different growth orientations.

The researchers used computational analysis via molecular dynamics and density functional theory simulations to determine the structural and electronic properties of a-type basal edge dislocations along the <1-100> direction in GaN. Dislocations along this direction are common in semipolar growth orientations.

The study was based on three models with different core configurations. The first consisted of three nitrogen (N) atoms and one gallium (Ga) atom for the Ga polarity; the second had four N atoms and two Ga atoms; the third contained two N atoms and two Ga core-associated atoms. Molecular dynamic calculations were performed using approximately 15,000 atoms for each configuration.

The researchers found that the N polarity configurations exhibited significantly more states in the bandgap compared to the Ga polarity ones, with the N polar configurations presenting smaller bandgap values.

"There is a connection between the smaller bandgap values and the great number of states inside them," said Kioseoglou. "These findings potentially demonstrate the role of nitrogen as a major contributor to dislocation-related effects in GaN-based devices."


The article, "Structural and electronic properties of a-edge dislocations along <1-100> in GaN," is authored by Stefanos Giaremis, Philomela Komninou, Imad Belabbas, Jun Chen and Joseph Kioseoglou. The article appeared in Journal of Applied Physics June 26, 2018, (DOI: 10.1063/1.5034198) and can be accessed at


The Journal of Applied Physics is an influential international journal publishing significant new experimental and theoretical results of applied physics research. See

Media Contact

Julia Majors


Julia Majors | EurekAlert!
Further information:

More articles from Physics and Astronomy:

nachricht Non-volatile control of magnetic anisotropy through change of electric polarization
12.11.2019 | Kanazawa University

nachricht Thorium superconductivity: Scientists discover new high-temperature superconductor
11.11.2019 | Moscow Institute of Physics and Technology

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A new quantum data classification protocol brings us nearer to a future 'quantum internet'

The algorithm represents a first step in the automated learning of quantum information networks

Quantum-based communication and computation technologies promise unprecedented applications, such as unconditionally secure communications, ultra-precise...

Im Focus: Distorted Atoms

In two experiments performed at the free-electron laser FLASH in Hamburg a cooperation led by physicists from the Heidelberg Max Planck Institute for Nuclear physics (MPIK) demonstrated strongly-driven nonlinear interaction of ultrashort extreme-ultraviolet (XUV) laser pulses with atoms and ions. The powerful excitation of an electron pair in helium was found to compete with the ultrafast decay, which temporarily may even lead to population inversion. Resonant transitions in doubly charged neon ions were shifted in energy, and observed by XUV-XUV pump-probe transient absorption spectroscopy.

An international team led by physicists from the MPIK reports on new results for efficient two-electron excitations in helium driven by strong and ultrashort...

Im Focus: A Memory Effect at Single-Atom Level

An international research group has observed new quantum properties on an artificial giant atom and has now published its results in the high-ranking journal Nature Physics. The quantum system under investigation apparently has a memory - a new finding that could be used to build a quantum computer.

The research group, consisting of German, Swedish and Indian scientists, has investigated an artificial quantum system and found new properties.

Im Focus: Shedding new light on the charging of lithium-ion batteries

Exposing cathodes to light decreases charge time by a factor of two in lithium-ion batteries.

Researchers at the U.S. Department of Energy's (DOE) Argonne National Laboratory have reported a new mechanism to speed up the charging of lithium-ion...

Im Focus: Visible light and nanoparticle catalysts produce desirable bioactive molecules

Simple photochemical method takes advantage of quantum mechanics

Northwestern University chemists have used visible light and extremely tiny nanoparticles to quickly and simply make molecules that are of the same class as...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

High entropy alloys for hot turbines and tireless metal-forming presses

05.11.2019 | Event News

Smart lasers open up new applications and are the “tool of choice” in digitalization

30.10.2019 | Event News

International Symposium on Functional Materials for Electrolysis, Fuel Cells and Metal-Air Batteries

02.10.2019 | Event News

Latest News

Using mountains for long-term energy storage

12.11.2019 | Power and Electrical Engineering

“KaSiLi”: Better batteries for electric cars “Made in Germany”

12.11.2019 | Power and Electrical Engineering

How the Zika virus can spread

11.11.2019 | Life Sciences

Science & Research
Overview of more VideoLinks >>>