N. Bouarissa

Electronic structure of pseudobinary semiconductor alloys InxGa1−x and InAsxSb1−x

A method calculating detailed electronic properties of the anionic and cationic pseudobinary InxGa1−xSb and InAsxSb1−x semiconductor alloys is presented. The technique begins with realistic band structures obtained for the constituent compounds by fitting the band-gap symmetry-point energies to experimental data within the pseudopotential scheme. Then the virtual crystal approximation which incorporates compositional disordered as an effective potential is used to calculate the alloys band structures and charge densities. Detailed comparison between the theoretical predictions and experimental data demonstrate the quantitative nature of the method. Bowing parameters for the Ω, X, and L gaps are in good agreement with the experimental results.

Energy gap versus alloy composition and temperature in GaxIn1-xSb

A simple adjusted pseudopotential form factor combined with the virtual crystal approximation and incorporating the compositional disorder as an effective potential for the alloy Ga x In 1-x Sb has been used in order to calculate the dependence of the direct and indirect band gaps on molar fraction and temperature. The obtained results compare reasonably well with available experimental data. The bowing parameter decreases with increasing temperature. The values of the temperature coefficients are nonlinearly dependent on molar composition and dependent on the temperature range.

Band structure calculations of Ga1 − xAlxAs, GaAs1 − xPx and AlAs under pressure

Abstract The band structure of Ga 1 − x Al x As and GaAs 1 − x P x cation and anion alloys respectively are calculated within the virtual crystal approximation using an adjusted empirical pseudopotential scheme, which incorporates compositional disorder as an effective potential. It is shown that the present theory, which is free from any additional parameter, satisfactorily produces the band-gap bowings. The effect of alloying was correlated to the effect of positive and negative pressure in AlAs. We have also calculated the variation of the ionicity of these alloys under pressure, the results are linked to the high pressure phase transitions.

Transferable Non‐Orthogonal Tight‐Binding Model for Silicon

We present a transferable tight-binding model; the electronic band structures and density of states of silicon in several cubic forms are obtained, within a nonorthogonal basis. We have fitted the nonorthogonal tight-binding model of silicon with a minimal (s, p) basis. Using a numerical procedure, our parameters were fitted to LMTO band structures in different crystalline phases of silicon (f.c.c., b.c.c., s.c., and h.c.p.). Such fits were performed to obtain a model that we judged to be accurate and should be applicable to many other systems. In addition to a very good fit to the electronic properties of Si in different bulk crystal structures our TB parameters describe very well the elastic constants and the optical phonon frequency at the zone-center in crystalline silicon.

The alloying and pressure dependence of band gaps in GaAs and GaAsxP1−x

Abstract We have calculated the electronic band structures for GaAsxP1−x alloy system using the empirical nonlocal pseudopotential method. The nonlocality of the potential is described by the Gaussian model. We find that the energy gap varies sublinearly with x, with the direct-indirect transition occuring at x = 0.58. The dependence on hydrostatic pressure of the direct and indirect energy band gaps of GaAs have been calculated with the pseudopotential method. The optimized nonlocal pseudopotential reproduce the energy gap dependence with pressure within a small deviation compared to the experimental values.

Calculation of the electronic and elastic properties of carbon

By accurately fitting tight-binding parameters to ab initio band structures from different tetrahedral volumes, tight-binding parameters have been developed for carbon. The model has scaling form similar to the tight-binding Hamiltonian of Xu et al. However, the properties of the higher-coordinated metallic structure are well described by the model in addition to those of the lower-coordinated covalent structures. This one reproduces accurately the band structures of carbon polytypes and gives a good description of the elastic constants for carbon in diamond structure. Results for phonon frequencies in crystalline carbon are also presented.

Electronic structure of GaSb under temperature and pressure effects

Abstract The variation of the direct and indirect band gaps of GaSb with pressure and temperature has been calculated using the adjacent empirical pseudopotential method. Our results for most of the gaps agree well with those of the experimental one. The contribution of the thermal expansion term to the temperature dependence of the gaps has been estimated and the results show that this effect is more important for the direct gap than the indirect one.

Electronic structure of the quaternary alloy GaxIn1-xAsyP1-y

Abstract A method for calculating the electronic structure of the quaternary alloy GaxIn1−xAsyP1−y is presented. We have used the empirical pseudopotential method coupled with the virtual crystal approximation, which incorporates the compositional disorder as an effective potential. The electronic structure are studied for GaxIn1−xAsyP1−x (x = 0.5; y= 0.5) and GaxIn1−xAsyP1−y lattice matched to InP as well as GaAs. Good agreement with experiment is obtained for the calculated values of the direct energy gap and the bowing parameter at the λ point of the InP-lattice-matched quaternary alloy.