FP-LAPW calculations of ground state properties for AlN, GaN and InN compounds (original) (raw)
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Exact-exchange calculations of the electronic structure of AlN, GaN and InN
Computer Physics Communications, 2005
The electronic structure of the zincblende (ZB) phase of AlN, GaN and InN has been investigated by using the exact-exchange (EXX) Kohn-Sham density functional theory, with the Ga 3d and In 4d electrons treated both as valence states and as part of the frozen core. Our EXX bandgaps for AlN and GaN (obtained with the semicore Ga 3d electrons included as core states) are found to be in good agreement with previous EXX calculations, GW results and available experimental data. When the semicore d electrons are treated as valence states, the EXX bandgap of ZB-GaN is found to be in excellent agreement with the GW results. However, both the EXX and GW bandgaps are about 0.4 eV smaller than experiment. For InN, where the application of the GW approach is problematic, due the negative LDA bandgap, the EXX approach allows for a fully consistent treatment. Contrary to common belief, the removal of the self-interaction, by the EXX approach, does not account for the large discrepancies between the LDA (or GGA) results and experiment for the position of the semicore d bands. .jo (A. Qteish). ory approach [2,3] to calculate the electronic structure of AlN, GaN and InN. The semicore d electrons of Ga and In are treated both as valence states and as part of the frozen core.
Physical Review B, 2001
A number of diverse bulk properties of the zinc-blende and wurtzite III-V nitrides AlN, GaN, and InN, are predicted from first principles within density-functional theory using the plane-wave ultrasoft pseudopotential method, within both the local density approximation ͑LDA͒ and generalized gradient approximation ͑GGA͒ to the exchange-correlation functional. Besides structure and cohesion, we study formation enthalpies ͑a key ingredient in predicting defect solubilities and surface stability͒, spontaneous polarizations and piezoelectric constants ͑central parameters for nanostructure modeling͒, and elastic constants. Our study bears out the relative merits of the two density-functional approaches in describing diverse properties of the III-V nitrides ͑and of the parent species N 2 , Al, Ga, and In͒. None of the two schemes gives entirely successful results. However, the GGA associated with the multiprojector ultrasoft pseudopotential method slightly outperforms the LDA overall as to lattice parameters, cohesive energies, and formation enthalpies of wurtzite nitrides. This is relevant to the study of properties such as polarization, vibrational frequencies, elastic constants, nonstochiometric substitution, and absorption. A major exception is the formation enthalpy of InN, which is underestimated by the GGA ͑ϳ0 vs Ϫ0.2 eV͒.
2009
First principles calculations are carried out for AlN, GaN, InN, AlGaN and InGaN in various crystal structures. The computational method used to investigate the structural and the electronic properties is the full potential linear muffin-tin orbital (FP-LMTO) augmented by a plane-wave basis (PLW). Exchange-correlation has been accounted for within LDA using the exchange-correlation potential calculated by Vosko et al. and
Physical Review B, 2001
A number of diverse bulk properties of the zincblende and wurtzite III-V nitrides AlN, GaN, and InN, are predicted from first principles within density functional theory using the plane-wave ultrasoft pseudopotential method, within both the LDA (local density) and GGA (generalized gradient) approximations to the exchange-correlation functional. Besides structure and cohesion, we study formation enthalpies (a key ingredient in predicting defect solubilities and surface stability), spontaneous polarizations and piezoelectric constants (central parameters for nanostructure modeling), and elastic constants. Our study bears out the relative merits of the two density functional approaches in describing diverse properties of the III-V nitrides (and of the parent species N2, Al, Ga, and In), and leads us to conclude that the GGA approximation, associated with high-accuracy techniques such as multiprojector ultrasoft pseudopotentials or modern all-electron methods, is to be preferred in the study of III-V nitrides.
Zinc-blende GaN: ab initio calculations
Materials Science and Engineering: B, 1997
The purpose of this paper is to contribute, on a theoretical basis, an understanding of future wide-gap device concepts and applications based on III-V nitride semiconductors. The electronic properties of zinc-blende structure GaN and their (110), and surfaces are investigated using ab initio calculations based on the full potential linear augmented plane-wave (FPLAPW) method within the large unit cell approach, and on the molecular Gaussian-92 code. Lattice constant, cohesive energy, bulk modulus are obtained from total energy calculations. Light-hole and heavy-hole effective masses along and directions and electron masses at G point are extracted from band structure calculations and compared with previous ones based on pseudopotential methods. The hydrostatic pressure dependence of the GG, GX and GL energy gaps are also obtained. Comparing our band structure and 'molecular cluster' calculations, the relaxations of the surfaces are found to be mostly determined by local rehybridization or valence effects and are basically independent of energy band features. © 1997 Elsevier Science S.A.
Calculated Electronic and Related Properties of Wurtzite and Zinc Blende Gallium Nitride (GaN)
We report calculated, electronic and related properties of wurtzite and zinc blende gallium nitrides (w-GaN, zb-GaN). We employed a local density approximation (LDA) potential and the linear combination of atomic orbital (LCAO) formalism. The implementation of this formalism followed the Bagayoko, Zhao, and Williams (BZW) method, as enhanced by Ekuma and Franklin (BZW-EF). The calculated electronic and related properties, for both structures of GaN, are in good agreement with corresponding, experimental data, unlike results from most previous ab initio calculations utilizing a density functional theory (DFT) potential. These results include the electronic energy bands, the total and partial densities of states (DOS and pDOS), and effective masses for both structures. The calculated band gap of 3.29 eV, for w-GaN, is in agreement with experiment and is an average of 1.0 eV larger than most previous ab-initio DFT results. Similarly, the calculated band gap of zb-GaN of 2.9 eV, for a r...
Physical Review B, 1999
We have performed density-functional calculations for III-V nitrides using the pseudopotential plane-wave method where the d states of the Ga and In atoms are included as valence states. Results obtained using both the local-density approximation ͑LDA͒ and the generalized gradient approximation ͑GGA͒ for the exchangecorrelation functional are compared. Bulk properties, including lattice constants, bulk moduli and derivatives, cohesive energies, and band structures are reported for AlN, GaN, and InN in zinc-blende and wurtzite structures. We also report calculations for some of the bulk phases of the constituent elements. The performance of our pseudopotentials and various convergence tests are discussed. We find that the GGA yields improved physical properties for bulk Al, N 2 , and bulk AlN compared to the LDA. For GaN and InN, essentially no improvement is found: the LDA exhibits overbinding, but the GGA shows a tendency for underbinding. The degree of underbinding and the overestimate of the lattice constant as obtained within the GGA increases on going from GaN to InN. Band structures are found to be very similar within the LDA and GGA. For the III-V nitrides, the GGA therefore does not offer any significant advantages; in particular, no improvement is found with respect to the band-gap problem. ͓S0163-1829͑99͒06107-X͔
First-principles prediction of the structural and electronic properties of GaxY1−xN compounds
Computational Materials Science, 2014
To investigate the structural and electronic properties of zinc blende GaN x As 1−x alloys, we performed full-potential linearized augmented plane wave (FP-LAPW) calculations based on density functional theory. We assessed GaN x As 1−x alloys for 0≤x≤1 using 16-atom special quasi-random structures. The generalized gradient approximation (GGA) of Wu and Cohen was used as the exchange correlation potential to calculate the structural and electronic properties of GaN x As 1−x. In addition, the alternative GGA proposed by Engel and Vosko and the modified Becke-Johnson potential were used for better reproduction of the band structure and electronic properties. The equilibrium lattice parameters and bulk modulus were calculated and analyzed for binary and ternary alloys. The lattice constants for GaN x As 1 −x positively deviate from Vegard's law with an upward bowing parameter of −0.4708 Å. All our materials are direct-bandgap semiconductors for which the valence band maximum is located at Γ v and the conduction band minimum at Γ c. We observed that the direct bandgap of GaN x As 1−x increases nonlinearly with x. To shed light on the bandgap trend for increasing nitrogen concentrations in GaN x As 1−x , we used the atoms-in-molecule formalism. Special attention was paid to the increase in charge transfer for the nitrogen atom and to ionicity as a function of increasing x concentration.
An oversight of some previous density functional calculations of the band gaps of wurtzite and cubic InN and of wurtzite GaN by Rinke et al. [Appl. Phys. Lett. 89,161919, 2006] led to an inaccurate and misleading statement relative to limitations of density functional theory (DFT) for the description of electronic properties of these materials. These comments address this statement. In particular, they show that some local density approximation (LDA) calculations have correctly described or predicted electronic and related properties of these systems [Phys. Rev. B 60, 1563, 1999; J. Appl. Phys. 96, 4297, 2004, and 97, 123708, 2005]. These successful calculations solved self-consistently the system of equations defining LDA, i.e., the Kohn-Sham equation and the equation giving the ground state charge density in terms of the wave functions of the occupied states.
Materials Science in Semiconductor Processing, 2013
To investigate the structural and electronic properties of zinc blende GaN x As 1−x alloys, we performed full-potential linearized augmented plane wave (FP-LAPW) calculations based on density functional theory. We assessed GaN x As 1−x alloys for 0≤x≤1 using 16-atom special quasi-random structures. The generalized gradient approximation (GGA) of Wu and Cohen was used as the exchange correlation potential to calculate the structural and electronic properties of GaN x As 1−x . In addition, the alternative GGA proposed by Engel and Vosko and the modified Becke-Johnson potential were used for better reproduction of the band structure and electronic properties. The equilibrium lattice parameters and bulk modulus were calculated and analyzed for binary and ternary alloys. The lattice constants for GaN x As 1 −x positively deviate from Vegard's law with an upward bowing parameter of −0.4708 Å. All our materials are direct-bandgap semiconductors for which the valence band maximum is located at Γ v and the conduction band minimum at Γ c . We observed that the direct bandgap of GaN x As 1−x increases nonlinearly with x. To shed light on the bandgap trend for increasing nitrogen concentrations in GaN x As 1−x , we used the atoms-in-molecule formalism. Special attention was paid to the increase in charge transfer for the nitrogen atom and to ionicity as a function of increasing x concentration.