https://doi.org/10.1140/epjb/e2008-00314-7
Optical and piezoelectric anomalies of ordered (Sc, Ga) N and (Sc, In) N ternaries
Department of Physical Sciences, Jordan University of Science and Technology, Irbid-22110, Jordan
Corresponding author: a alsaad11@just.edu.jo
Received:
19
February
2008
Revised:
1
June
2008
Published online:
22
August
2008
Theoretical results are presented regarding the
incorporation of Scandium into wurtzite GaN and InN binaries. The electric,
optical and piezoelectric properties of the resulting ScGaN and ScInN
systems are reported by using first-principles Local-density approximation
(LDA) within density functional theory (DFT), Berry phase approach within
modern theory of polarization and phonon calculations within the density
functional perturbation theory. Our results predict the existence of
breaking-symmetry structural phase transition in ordered
Sc0.5Ga0.5N and Sc0.5In0.5N alloys when subjected to a
compressive or tensile strain. Moreover, our results demonstrate the existence of symmetry
preserving pressure-induced isostructural phase transitions in ordered ScGaN
and ScInN systems for different Sc concentrations. It has been shown that
the existence of isostructural phase transitions leads to dramatic changes
in optical, acoustic, and piezoelectric properties of ordered ScGaN and
ScInN systems under high pressure. In particular, this study demonstrates
that the existence of first-order isostructural phase transitions in
Sc1Ga1N2 at a critical hydrostatic pressure of 12.3 GPa leads
to a huge enhancement of piezoelectricity (i.e., the e33 piezoelectric
coefficient adopts a huge value as large as 13 C/m
. In addition, It
has been shown that ordered Sc0.5Ga0.5N and Sc0.5In0.5N
alloys exhibit tremendous piezoelectric response, associated with a
breaking-symmetry phase transition from nonpolar 
/mcc
space
group to a polar mc
structure, at fixed Ga, In and Sc
compositions, as a function of the in-plane compressive and tensile strains.
We also reveal the reason behind, and consequences of, these unusual
properties associated with the strain-induced and pressure-induced
structural phase transitions in the novel ScGaN and ScInN ordered
structures.
PACS: 71.15.-m – Methods of electronic structure calculations / 71.15.Mb – Density functional theory, local density approximation, gradient and other corrections / 71.20.-b – Electron density of states and band structure of crystalline solids / 71.15.Dx – Computational methodology (Brillouin zone sampling, iterative diagonalization, pseudopotential construction)
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2008
