Local coordination, structural softening, and polarization-switching energetics in Sc-alloyed GaN
Abstract
Sc-alloyed wurtzite nitrides exhibit strongly tunable electromechanical and ferroelectric properties, yet the relationship between their lattice evolution and local bonding environment remains insufficiently established, particularly in ScxGa1−xN. Here, we investigate the structural and local bonding evolution of ScxGa1−xN across the dilute-to-intermediate composition range by combining X-ray diffraction, Sc K-edge X-ray absorption near edge structure (XANES), extended X-ray absorption fine structure (EXAFS) and first-principles calculations. Sc incorporation produces an anisotropic lattice expansion and a progressive reduction in the c/a ratio. XANES and EXAFS reveal a concurrent modification of the local environment around Sc, with the effective Sc-N coordination number increasing from 4.1(4) to 4.5(2) and the average Sc-N bond length increasing from 2.045(7) to 2.081(8)Å over x=0.06-0.26. The local response is accompanied by a reduction in the Sc K-edge pre-edge intensity, consistent with a gradual reduction of the local tetrahedral asymmetry. First-principles calculations show that these structural changes are associated with site-selective distortions around Sc and progressive flattening of the structural energy landscape. The calculated intrinsic polarization-switching barrier decreases from 24.2 to 19.0 meV/Å3 with increasing Sc content, while the calculated piezoelectric stress coefficient (e33) increases from 0.82 to 1.66~C/m2 and elastic constant (C33) decreases from 380 to 227~GPa, resulting in an increase of piezoelectric strain coefficient (d33) from 2.99 to 12.46~pC/N. These results show that Sc incorporation progressively modifies the local coordination environment and structural energetics of ScGaN while the long-range wurtzite structure remains preserved over the investigated composition range.
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BibTeX
@misc{kalal2026local,
title = {{Local coordination, structural softening, and polarization-switching energetics in Sc-alloyed GaN}},
author = {Shailesh Kalal and Gueorgui Kostov Gueorguiev and Martin Magnuson and Edward Ferraz de Almeida Junior and Rohini Sanikop and Sagar Jathar and Per Sandström and Ray-Hua Horng and Jens Birch and Per Eklund and Ching-Lien Hsiao},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.05000},
eprint = {2609.05000},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.05000},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Local coordination, structural softening, and polarization-switching energetics in Sc-alloyed GaN
AU - Shailesh Kalal
AU - Gueorgui Kostov Gueorguiev
AU - Martin Magnuson
AU - Edward Ferraz de Almeida Junior
AU - Rohini Sanikop
AU - Sagar Jathar
AU - Per Sandström
AU - Ray-Hua Horng
AU - Jens Birch
AU - Per Eklund
AU - Ching-Lien Hsiao
PY - 2026
DA - 2026/09/04
PB - arXiv
DO - 10.48550/arxiv.2609.05000
UR - https://arxiv.org/abs/2609.05000
AB - Sc-alloyed wurtzite nitrides exhibit strongly tunable electromechanical and ferroelectric properties, yet the relationship between their lattice evolution and local bonding environment remains insufficiently established, particularly in Sc_xGa_1−xN. Here, we investigate the structural and local bonding evolution of Sc_xGa_1−xN across the dilute-to-intermediate composition range by combining X-ray diffraction, Sc K-edge X-ray absorption near edge structure (XANES), extended X-ray absorption fine structure (EXAFS) and first-principles calculations. Sc incorporation produces an anisotropic lattice expansion and a progressive reduction in the c/a ratio. XANES and EXAFS reveal a concurrent modification of the local environment around Sc, with the effective Sc-N coordination number increasing from 4.1(4) to 4.5(2) and the average Sc-N bond length increasing from 2.045(7) to 2.081(8)Å over x=0.06-0.26. The local response is accompanied by a reduction in the Sc K-edge pre-edge intensity, consistent with a gradual reduction of the local tetrahedral asymmetry. First-principles calculations show that these structural changes are associated with site-selective distortions around Sc and progressive flattening of the structural energy landscape. The calculated intrinsic polarization-switching barrier decreases from 24.2 to 19.0 meV/Å^3 with increasing Sc content, while the calculated piezoelectric stress coefficient (e_33) increases from 0.82 to 1.66~C/m^2 and elastic constant (C_33) decreases from 380 to 227~GPa, resulting in an increase of piezoelectric strain coefficient (d_33) from 2.99 to 12.46~pC/N. These results show that Sc incorporation progressively modifies the local coordination environment and structural energetics of ScGaN while the long-range wurtzite structure remains preserved over the investigated composition range.
ER -