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Papers by Mohamed FERHAT
Superlattices and Microstructures, 2019
The ternary III-Nitride AlxGa1-xN ternary is one of the paradigm materials that have recently rev... more The ternary III-Nitride AlxGa1-xN ternary is one of the paradigm materials that have recently revolutionized lighting technology in the ultraviolet spectrum. A systematic investigation of the GaN-AlN system using ab initio evolutionary algorithm evidence that AlxGa1-xN alloys exist in ordered ground-state structure at ambient conditions. Cubic (AlGa3N4 (x=0.25), Al3GaN4(x=0.75)) and tetragonal (AlGaN2 (x=0.5)) are found thermodynamically quite or nearly stable. Computed elastic constants and phonons show that these phases are mechanically and dynamically stable. Using state-of-the-art LDA-1/2 approach we determine the direct band gap bowing of AlGaN alloys. We found a downward bowing parameter of b∼1.39eV over the entire composition range. Furthermore the optical band gap bowing is found composition-dependent. For x = 0.5, our theoretical analysis divulges that chemical effects are the main factor leading to b parameter.
Superlattices and Microstructures, 2009
We have performed ab initio self-consistent calculations based on the full potential linear augme... more We have performed ab initio self-consistent calculations based on the full potential linear augmented plane-wave method (FP-LAPW) with the local density approximation (LDA) and the Generalised Gradient Approximation (GGA) to investigate the relativistic effects, on the structural, and transport properties of III-V compounds. We found that the stabilisation (destabilisation) of s, p * (p, d) orbital energies (i) reduces the lattice parameters of III-V compounds, considerably reduces the band gaps of the III-V compounds, (ii) reduces the effective masse, and (iii) induces strong spin orbit splitting of heavier III-V compounds. Furthermore we circumvent the negative gap problem by combining non relativistic and Engel-Vosko approximations. These approaches open the gap of the most III-V compounds, and leads to a realistic band structure.
Physical Review B, 2006
We have performed ab initio self-consistent calculations based on the full potential linear augme... more We have performed ab initio self-consistent calculations based on the full potential linear augmented planewave method with the generalized gradient approximation to investigate the structural and the electronic properties of the less known bismuth III-V compounds: BBi, AlBi, GaBi, and InBi. Ground state parameters are computed and compared with available theoretical and experimental works. The zinc-blende phase is found to be the most stable for BBi, AlBi, and GaBi, while InBi prefers the tetragonal PbO structure. The relativistic contraction of the 6s orbital of Bi has strong effect on the band structure of III-Bi compounds, which exhibits some features that differ considerably from those of typical III-V semiconductors. In particular, we found an inverted band gap, which reflects a semimetallic character of these systems. Their bonding nature is analyzed in terms of valence charge density transfer, showing three different natures of the bond. Besides, the calculated valence charge density for BBi shows an anomalous behavior characterized by a charge transfer toward the cation B atom, while the others III-Bi behave as the typical III-V compounds with a small charge transfer to the anion bismuth atom.
Cogent Physics, 2017
as soon as possible after acceptance. Copyediting, typesetting, and review of the resulting proof... more as soon as possible after acceptance. Copyediting, typesetting, and review of the resulting proof will be undertaken on this manuscript before final publication of the Version of Record (VoR). Please note that during production and pre-press, errors may be discovered which could affect the content.
Applied Physics Letters, 2008
Superlattices and Microstructures, 2019
The ternary III-Nitride AlxGa1-xN ternary is one of the paradigm materials that have recently rev... more The ternary III-Nitride AlxGa1-xN ternary is one of the paradigm materials that have recently revolutionized lighting technology in the ultraviolet spectrum. A systematic investigation of the GaN-AlN system using ab initio evolutionary algorithm evidence that AlxGa1-xN alloys exist in ordered ground-state structure at ambient conditions. Cubic (AlGa3N4 (x=0.25), Al3GaN4(x=0.75)) and tetragonal (AlGaN2 (x=0.5)) are found thermodynamically quite or nearly stable. Computed elastic constants and phonons show that these phases are mechanically and dynamically stable. Using state-of-the-art LDA-1/2 approach we determine the direct band gap bowing of AlGaN alloys. We found a downward bowing parameter of b∼1.39eV over the entire composition range. Furthermore the optical band gap bowing is found composition-dependent. For x = 0.5, our theoretical analysis divulges that chemical effects are the main factor leading to b parameter.
Superlattices and Microstructures, 2009
We have performed ab initio self-consistent calculations based on the full potential linear augme... more We have performed ab initio self-consistent calculations based on the full potential linear augmented plane-wave method (FP-LAPW) with the local density approximation (LDA) and the Generalised Gradient Approximation (GGA) to investigate the relativistic effects, on the structural, and transport properties of III-V compounds. We found that the stabilisation (destabilisation) of s, p * (p, d) orbital energies (i) reduces the lattice parameters of III-V compounds, considerably reduces the band gaps of the III-V compounds, (ii) reduces the effective masse, and (iii) induces strong spin orbit splitting of heavier III-V compounds. Furthermore we circumvent the negative gap problem by combining non relativistic and Engel-Vosko approximations. These approaches open the gap of the most III-V compounds, and leads to a realistic band structure.
Physical Review B, 2006
We have performed ab initio self-consistent calculations based on the full potential linear augme... more We have performed ab initio self-consistent calculations based on the full potential linear augmented planewave method with the generalized gradient approximation to investigate the structural and the electronic properties of the less known bismuth III-V compounds: BBi, AlBi, GaBi, and InBi. Ground state parameters are computed and compared with available theoretical and experimental works. The zinc-blende phase is found to be the most stable for BBi, AlBi, and GaBi, while InBi prefers the tetragonal PbO structure. The relativistic contraction of the 6s orbital of Bi has strong effect on the band structure of III-Bi compounds, which exhibits some features that differ considerably from those of typical III-V semiconductors. In particular, we found an inverted band gap, which reflects a semimetallic character of these systems. Their bonding nature is analyzed in terms of valence charge density transfer, showing three different natures of the bond. Besides, the calculated valence charge density for BBi shows an anomalous behavior characterized by a charge transfer toward the cation B atom, while the others III-Bi behave as the typical III-V compounds with a small charge transfer to the anion bismuth atom.
Cogent Physics, 2017
as soon as possible after acceptance. Copyediting, typesetting, and review of the resulting proof... more as soon as possible after acceptance. Copyediting, typesetting, and review of the resulting proof will be undertaken on this manuscript before final publication of the Version of Record (VoR). Please note that during production and pre-press, errors may be discovered which could affect the content.
Applied Physics Letters, 2008