Hamza Abid

Tight binding calculation of electronic properties of ternary alloy ZnSxSe1−x

Abstract Using an sp 3 s ∗ empirical tight binding method, we calculate energy band gap and electronic band structure of the zinc-blende ternary alloy ZnS x Se 1− x . The band gap composition is calculated using an extended version of the virtual crystal approximation, which introduce an empirical correction factor that takes into account the non-linear dependence of the band gap with the composition. The results compare well with the experimental data. The ionicity character and the refractive index are also calculated.

FIRST-PRINCIPLE CALCULATION OF STRUCTURAL AND ELECTRONIC PROPERTIES OF ZINC-BLENDE ByAlxGa1-x-yN MATCHED TO AlN SUBSTRATE

The full-potential linearized augmented plane wave method (FP-LAPW) within density functional theory, using the generalized gradient approximation, is used to study the structural and electronic properties of zinc-blende ByAlxGa1-x-yN quaternary alloys that match the lattice of an AlN substrate. The range of compositions, for which the lattice of the alloy matches AlN, is determined. Our calculated band structure, density of states, electron density and lattice parameter for ByAlxGa1-x-yN allow to accurately evaluate the profound effect that the incorporation of small amounts of Boron have on structural and electronic properties of AlxGa1-xN alloys. A comparison of the ground state properties with the available experimental and theoretical data is made for the compounds related to ByAlxGa1-x-yN and of the AlxGa1-xN alloys. The results show a strong dependence of the band gap (as well as the lattice parameter) on the Boron content, which might make ByAlxGa1-x-yN materials promising and useful for optoelectronic applications.

Theoretical analysis of disorder effects on electronic and optical properties of the quaternary alloy Ga1−xAlxAsySb1−y

Abstract The effects of structural and chemical disorder on electronic and optical properties of GaAlAsSb quaternary alloy are studied on the basis of a modified virtual crystal approximation calculated within a simple tight-binding sp 3 s ∗ 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 and other recent calculations. The essential features of structure and disorder-induced changes in electronic and optical structure are exhibited in the sp 3 s ∗ results by two characterization parameters: the subband energy spacing and the density of states. The changes in each of them are found to depend on the interrelated trends of structure and disorder effects.

Full Potential Calculation of the Band-Gaps in GaP/GaN Superlattices

The present paper deals with the electronic properties of GaP and GaN zinc-blende/zincblende superlattices using the plane wave version of the full potential linear muffin-tin orbital (FPLMTO) method, which allows an accurate treatment of the interstitial regions. It is found that bowing, which is known to occur for ternary GaPN dilute nitrides, is absent from GaP/GaN 〞dilute nitride〞 superlattices with N concentrations greater than 7%, but it can be obtained in these same superlattices for high nitride concentrations.

Electronic and optical properties of ternary alloys ZnxCd1−xS, ZnxCd1−xSe, ZnSxSe1−x, MgxZn1−xSe

Abstract The empirical pseudopotential method (EPM) within the virtual crystal approximation (VCA) is used to calculate the electronic and optical properties of ternary alloys ZnxCd1−xS, ZnxCd1−xSe, ZnSxSe1−x and MgxZn1−xSe. The alloy band structures and energy gaps are calculated using VCA which incorporates the compositional disorder as an effective potential. The calculated band structures for the ZnxCd1−xS, ZnxCd1−xSe and ZnSxSe1−x alloys show a direct band gap in the whole range of the concentration except for the MgxZn1−xSe alloy which presents a crossover from the direct gap to the indirect one.Also the dependence of the refractive index on the concentration is calculated for each ternary alloy. This parameter is found to depend nonlinearly on the alloy concentration. A detailed comparison of our results with experimental data and works of other authors has led to a good agreement.

Correlation between high-pressure effects and alloying in GaP and AlP

Abstract The variation of the direct and indirect band gap of GaP and AlP has been calculated using the adjusted empirical pseudopotential method. The gap varies sublinearly with pressure but linearly with lattice constant. These results are discussed in the light of experimental results. The direct band gap increases with increasing pressure, whereas the indirect gap decreases. The effect of high pressure is correlated with the effect of alloying in GaxAl1 − xP.