Calculation of electronic and optical properties of Zn-based II–VI semiconductors

AbstractZnSe and ZnS are the prototype II–VI semiconductors and their cubic phase, which occurs naturally as a mineral, has been called the zinc-blende structure. ZnSe has received particular attention as a blue-lasing material and tremendous experimental efforts have been made to fabricate a sustainable ZnSe blue laser. On the other hand, the ternary system ZnSxSe1−x is a good candidate for developing optoelectronic devices such as light emitting diodes (LEDs) or semiconductor lasers. It is also used as waveguides and confinement layers in laser diodes (LDs).In the present study, we have computed the electronic and optical properties of ZnSe, ZnS and ZnSxSe1−x using the local model pseudopotential method under the VCA. A central aim of this study is to present the electronic and optical properties of the materials of interest in the zinc-blende structure

Investigated optical and elastic properties of Porous silicon: Theoretical study

Link to publisher's homepage at www.elsevier.comCompatibility between experimental and theoretical works is achieved. Empirical Pseudopotential Method (EPM) is used to calculate the energy gap of Si which is found to be indirect. Features such as refractive index, optical dielectric constant, bulk modulus, elastic constants and short-range force constants have been investigated. In addition to the shear modulus, Young's modulus, Poisson's ratio and Lame's constants for both bulk Si (p = 0%) and Porous silicon (PS) are derived. The calculated results are found to be in good agreement with other experimental and theoretical ones. Also, the Debye temperature of PS is estimated from the average sound velocity. To our knowledge, the optical properties using specific models and elasticity of PS are reported for the first time

POSITRON STATES IN <font>Si</font>_1-x<font>Ge</font>_x ALLOYS: DEVIATION FROM VEGARD'S LAW

Electron-positron momentum densities along different crystallographic directions and positron bulk lifetime in Si 1-x Ge x alloys have been investigated within the pseudopotential formalism employing the independent particle model. Special attention has been given to the effect of the deviation of the alloy lattice parameters from Vegard's rule on the studied quantities. It is found that using Vegard's law leads to an underestimation of the total positron annihilation rate indicating therefore an overestimation of the positron bulk lifetime. This result could not be checked using the Siethoff relation (H. Siethoff, Phys. Stat. Sol.B205, R3 (1998)). Moreover, this relation predicts a monotonic dependence of the positron bulk lifetime on the alloy composition which disagrees with the positron lifetime measurement. </jats:p

ELECTRON MOMENTUM DENSITIES IN <font>Ga</font>_x<font>In</font>_1-x<font>As</font>_y<font>Sb</font>_1-y PROBED BY POSITRONS

Momentum densities of electron–positron pairs in cubic Ga x In 1-x As y Sb 1-y lattice matched to GaSb and InAs are studied for the first time to the best of our knowledge, with the aim of investigating the disorder and substrate effects on these quantities in the materials for interest. The electron wavefunction is calculated using the pseudopotential band model under the virtual crystal approximation with and without incorporating the effects of compositional variations. The calculations of the positron wavefunction is made in an identical manner, employing the point-core approximation for the ionic potential. It is found that while the electron–positron momentum densities in Ga x In 1-x As y Sb 1-y at x=0.50 are sensitive to the compositional disorder, they are not altered by the change of substrate. </jats:p