Electronic Properties Of Si Research Articles

Tetrahedrally symmetric DX-like states of substitutional donors in GaAs and AlxGa1-xAs alloys.

The structural and electronic properties of Si, Ge, Sn, S, Se, and Te substitutional donors in GaAs are examined via self-consistent pseudopotential calculations. Two distinct negatively charged DX-like deep donor states are found. The first has a broken-bond atomic configuration while the second arises from a symmetric ``breathing-mode'' relaxation around the impurity. The energies of the two configurations are especially close for Sn, Se, and Te donors. Experimental data on DX centers in ${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$As alloys are analyzed within this model.

Alkali adsorption on Si(111) surfaces: ab initio molecular dynamics studies

We have applied the Car-Parrinello method to determine structural and electronic properties of Si(111) in the presence of one monolayer of Na and Li. In both cases we find that the alkali adsorption stabilizes the 1 × 1 structure. In spite of the overall similarity in the chemical bonding, we find that the energitically favored adsorption sites are different. The substrate relaxation upon adsorption is minor in the case of Na and significant in the case of Li, where it also plays a crucial role in determining the equilibrium configuration. In both cases, small distortions in the uppermost Si layers are predicted along the [112] direction. Both systems turn out to be non-metallic, in agreement with the experimental data for Na. The surface band dispersion is in very good agreement with photoemission data on Si(111): Na and is predicted to be less flat for Si(111): Li

Activation analysis of rapid thermally annealed Si and Mg implanted semi-insulating GaAs

Electronic properties of Si and Mg implants in undoped semi-insulating GaAs are studied. The activation of the implants is achieved by rapid thermal annealing. The effects of implantation dose and anneal temperature on the measured electrical activity are investigated. In spite of similar depth distributions and implantation damage characteristics, a marked difference between the activations of the Si and the Mg ions is observed for the dose range considered (3×10^12 – 1×10^14 cm^–2). Lattice strain measurements performed by x-ray rocking curves indicate that the residual implantation damage after annealing is not largely responsible for this difference. The difference is mostly electronic in character, as also suggested by photoluminescence measurements. At high annealing temperatures, changes in the compensating properties of undoped semi-insulating GaAs are suspected, and are found to play an important role in the activation of implanted ions, affecting the n- and p-type dopants conversely.

Bond-angle relaxation and electronic structure of Si and Ge overlayers on (110) surfaces of III–V semiconductors

We present the results of a detailed study of relaxational and electronic properties of Si and Ge overlayers on nonpolar (110) surfaces of GaP, GaAs and GaSb. Systems ranging from one up to three homopolar monolayers on semi-infinite heteropolar substrates have been investigated. Structure optimizations, restricted to relaxational degrees of freedom of the overlayer system give rise to a “pseudoionic” outermost adlayer. This pseudoionicity is induced by the adlayer relaxation and by the heteropolarity of the substrates and it leads to pronounced splittings of the Ge and Si surface dangling bond bands similar to the anion- and cation-derived dangling bond bands of the clean relaxed substrate surfaces. Considering the surface layer relaxation asymmetry as a function of overlayer thickness, we find that three monolayers of adatoms are sufficient to decouple the surface from the interface in the overlayer systems. The total energy minimization and electronic structure calculations are carried out in the framework of a second-nearest neighbour empirical tight-binding model. The semi-infinite configurations are treated by scattering theory using one-particle Green functions.

Electronic properties of Si atomic-planar-doped GaAs/AlAs quantum well structures grown by MBE

Electronic properties of Si atomic-planar-doped GaAs/AlAs quantum well structures grown by MBE

Electronic properties of Si atomic-planar-doped GaAs/AlAs quantum well structures grown by MBE

Optical and electrical properties of silicon atomic-planar-doped (Si-PD) (GaAs) m /(AlAs) 5 rnultiquantura well structures ( m = 3–13; 30 periods) were measured to study the energy band structure in ultrathin quantum well layers. Reduction of photoluminescence intensity for m = 3 suggests the conduction band crossover (direct-indirect transition) in the GaAs region.

Application of a general self-consistency scheme in the linear combination of atomic orbitals formalism to the electronic and structural properties of Si and W.

We present a general self-consistency procedure formulated in momentum space for electronic structure and total-energy calculations of crystalline solids. It is shown that both the charge density and the change in the Hamiltonian matrix elements in each iteration can be calculated in a straight-forward fashion once a set of overlap matrices is computed. The present formulation has the merit of bringing the self-consistency problem for different basis sets to the same footing. The scheme is used to extend a first-principles pseudopotential linear combination of Gaussian orbitals method to full point-by-point self-consistency, without refitting of potentials. It is shown that the set of overlap matrices can be calculated very efficiently if we exploit the translational and space-group symmetries of the system under consideration. This scheme has been applied to study the structural and electronic properties of Si and W, prototypical systems of very different bonding properties. The results agree well with experiment and other calculations. The fully self-consistent results are compared with those obtained by a variational procedure [J. R. Chelikowsky and S. G. Louie, Phys. Rev. B 29, 3470 (1984)]. We find that the structural properties for bulk Si and W (both systems have no interatomic charge transfer) can be treated accurately by the variational procedure. However, full self-consistency is needed for an accurate description of the band energies.