A. Zaoui

Electronic structure of BN, BP and BAs

Abstract The empirical tight-binding method is used to investigate the electronic structure of the zinc-blende boron compounds BN, BP and BAs. Results are given for band structures, ionicity factors and elastic constants. The electronic structure of the boron compounds exhibits features that differ from those of the other III–V materials. In particular we found that these compounds are characterized by a strong cation-anion s–s repulsion effect. The calculated ionicity shows a weak charge transfer effect for BP and BAs which makes these compounds as the prototype covalent materials of the III–V family, while BN is found more ionic.

Electronic structure of the copper halides CuCl, CuBr and Cul

The electronic bands structure and density of states of zinc-blende CuCl, CuBr and CuI have been computed using the tight-binding method. These band structures have been used to calculate the valence and conduction band effective masses. The results are compared with other calculated and experimental values.

APPLICABILITY OF THE EMPIRICAL PSEUDOPOTENTIAL METHOD TO SEMICONDUCTORS WITH D VALENCE ELECTRONS

Abstract We use the empirical pseudopotential method to calculate the band structure and the density of states of materials with d valence electrons. We choose for this calculation a prototype of the I–VII semiconductors family: the copper chloride CuCl. The problematic d levels are avoided by developing the wave function in a high number of plane waves and using a strong nonlocal pseudopotential. The results are in good agreement with previous calculations and experimental data and show that the use of pseudopotentials is possible for the calculation of the band structures and related physical properties.

Molecular dynamics simulation of CuI using a three-body potential

A three-body potential coupled with a molecular dynamics method have been used to simulate structural properties of CuI in the zincblende and tetragonal phases. It is found that the diffusion constant is well reproduced for the α-phase of CuI using this model rather than a two-body potential. This study predicts also the presence of cation disorder at elevated temperature within the tetragonal phase of CuI.

Theoretical analysis of disorder effects on electronic and optical properties in InGaAsP quaternary alloy

The effects of structural and chemical disorder on electronic and optical properties of InGaAsP quaternary alloy are studied on the basis of a modified virtual crystal approximation calculated within a simple tight-binding sp3s* theory, which incorporates compositional disorder as an effective potential. Using a minimal set of fitting parameters, we show that such an approach provides analytical results for calculating energy gaps and bowing parameters. We show that the calculated bowing parameter agrees reasonably well with experimental data. The essential features of structure and disorder-induced changes in electronic and optical structure are exhibited in the sp3s* results by two characterization parameters: the subband energy spacings, and the density of states. The changes in each of them are found to depend on the interrelated trends of structure and disorder effects.

Electronic structure of AlxGa1 − xAs and GaPxAs1 − x alloys modified virtual crystal approximation calculation using sp3s* band structures

Abstract A simple tight-binding sp 3 s* model, which incorporates compositional disorder as an effective potential, is used for the calculations of the electronic structures of the semiconducting alloys Al x Ga 1 − x As and GaP x As 1 − x . Our results for various interesting quantities, including band-gap bowings and crossover of the band gaps of these two systems, are compared with the available data; a good agreement is found.

Exciton-polariton reflectance in CuI single crystals

Abstract We have measured the normal reflection spectrum of (1 1 0) cleaved faces of single crystals of CuI in the spectral range of the Z 12 (3058 meV) and Z 3 (3699 meV) exciton lines at the temperature of 95 K. We have fitted the experimental data by computing a non local dielectric function and taken into account various additional boundary conditions (ABC) as well as the dead layer model in a semi-infinite crystal. A quantitative agreement is obtained assuming the following values for the background dielectric constant e ∞ =7.2 and for the effective masses of the excitons M (Z 12 )=1.8 m 0 , M (Z 3 )=0.5 m 0 . These results do not depend on the choice of a particular ABC. The longitudinal-transverse exciton splitting energies deduced from the fit are: ω LT (Z 12 )=5.9 meV and ω LT (Z 3 )=2 meV.

The electronic structure of CuCl

We report a systematic study of the electronic properties of zinc-blende CuCl. The band structure, valence and conduction effective mass, density of states (DOS) and charges densities are calculated using the local density all-electron full-potential linearized augmented plane wave (FLAPW) method. Our results are in agreement with a host of theoretical and experimental data yielding a consistent description of electronic properties of this class of technologically important semiconductor compounds.

Calculation of the elastic properties of CuCl

Abstract The elastic constants of CuCl with zinc-blende structure are calculated by means of two processes. By using, first, a classical bond-orbital model based on the tight-binding method, and secondly, an approach which combines the latter model with an adjusted empirical pseudopotential method. The bond length d , bond polarity α p , bulk modulus B , elastic shear constants (C 11 -C 12 ) 2 , bond-stretching force constant α, bond-bending force constant β, internal displacement parameter ξ, effective atomic charge Z ∗ , transfer parameter β ∗ , transverse charge e T ∗ , and piezoelectric charge e p ∗ are calculated with both methods. The results are compared, with previous theoretical estimates and experiments.

On the high pressure structural phase transition and the chemical bonding in III–V compounds

We present an analysis of the ionicity factor as a function of hydrostatic pressure for GaP, GaAs, InP and InAs. This factor has been calculated by means of our recent model. We show that the structural phase transition, habitually predicted by a classical calculation of the total energy, can be easily seen from the behaviour of the bonding character. The results are compared with the experimental data with reasonable agreement.