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Łepkowski S.P.♦, Majewski J.A.♦, Jurczak G., Nonlinear elasticity in III-N compounds: ab-initio calculations,
PHYSICAL REVIEW B, ISSN: 1098-0121, Vol.72, pp.245201-0, 2005Abstract: We have studied the nonlinear elasticity effects in zinc-blende and wurtzite crystallographic phases of III-N compounds. Particularly, we have determined the pressure dependences of elastic constants in InN, GaN, and AlN by performing ab initio calculations in the framework of plane-wave pseudopotential implementation of the density-functional theory. The calculations have been performed employing two exchange-correlation functionals, one within the local density approximation and the other within the generalized gradient approximation. We have found that C11, C12 in zinc-blende nitrides and C11, C12, C13, C33 in wurtzite nitrides depend significantly on hydrostatic pressure. Much weaker dependence on pressure has been observed for C44 elastic constant in both zinc-blende and wurtzite phases. Further, we have examined the influence of pressure dependence of elastic constants on the pressure coefficient of light emission, dE / dP, in wurtzite InGaN / GaN and GaN / AlGaN quantum wells. We have shown that the pressure dependence of elastic constants leads to a significant reduction of dE / dP in nitride quantum wells. Finally, we have considered the influence of nonlinear elasticity of III-N compounds on the properties of hexagonal nitride quantum dots (QDs). For typical wurtzite GaN / AlN QDs, we have shown that taking into account pressure dependence of elastic constants results in the decrease of volumetric strain in the QD region by about 7%. Simultaneously, the average z component of the piezoelectric polarization in the QDs increases by 0.1 MV/ cm compared to the case when linear elastic theory is used. Both effects, i.e., decrease of volumetric strain as well as increase of piezoelectric field, decrease the band-to-band transition energies in the QDs. Keywords: III-V semiconductor, ab-initio calculation, nonlinear elasticity, third order elastic coefficient Affiliations:
Łepkowski S.P. | - | Institute of High Pressure Physics, Polish Academy of Sciences (PL) | Majewski J.A. | - | other affiliation | Jurczak G. | - | IPPT PAN |
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Łepkowski S.P.♦, Majewski J.A.♦, Jurczak G., Nonlinear elasticity in wurtzite GaN/AlN planar superlattices and quantum dots,
ACTA PHYSICA POLONICA A, ISSN: 0587-4246, Vol.108, No.5, pp.749-754, 2005Abstract: The elastic stiffness tensors for wurtzite GaN and AlN show a significant hydrostatic pressure dependence, which is the evidence of nonlinear elasticity of these compounds. We have examined how pressure dependence of elastic constants for wurtzite nitrides influences elastic and piezoelectric properties of GaN/AlN planar superlattices and quantum dots. Particularly, we show that built-in hydrostatic pressure, present in both quantum wells of the GaN/AlN superlattices and GaN/AlN quantum dots, increases significantly by 0.3–0.7 GPa when nonlinear elasticity is used. Consequently, the compressive volumetric strain in quantum wells and quantum dots decreases in comparison to the case of the linear elastic theory. However, the z-component of the built-in electric field in the quantum wells and quantum dots increases considerably when nonlinear elasticity is taken into account. Both effects, i.e., a decrease in the compressive volumetric strain as well as an increase in the built-in electric field, decrease the band-to-band transition energies in the quantum wells and quantum dots. Keywords: III-V semiconductor, nonlinear elasticity, third order elasic coefficient Affiliations:
Łepkowski S.P. | - | Institute of High Pressure Physics, Polish Academy of Sciences (PL) | Majewski J.A. | - | other affiliation | Jurczak G. | - | IPPT PAN |
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