Showing papers by "Alex Zunger published in 1983"
TL;DR: In this article, the electronic structure of six Cu-based ternary chalcopyrite semiconductors is calculated self-consistently for the first time within the density-functional formalism.
Abstract: The electronic structure of six Cu-based ternary chalcopyrite semiconductors is calculated self-consistently for the first time within the density-functional formalism. The chemical trends in the band structures, electronic charge densities, density of states, and chemical bonding are analyzed.
455 citations
TL;DR: The principle of conservation and transferability of chemical bonds explains the recent discovery by extended x-ray-absorption fine-structure measurements of two unequal anion-cation bond lengths in zinc-blende semiconductor alloys as discussed by the authors.
Abstract: The principle of conservation and transferability of chemical bonds explains the recent discovery by extended x-ray-absorption fine-structure measurements of two unequal anion-cation bond lengths ${R}_{\mathrm{AC}}$ and ${R}_{\mathrm{BC}}$ in ${A}_{x}{B}_{1\ensuremath{-}x}C$ zinc-blende semiconductor alloys despite the close adherence of the lattice constant to the average value (V\'egard rule). This bond alternation, manifested as a structural distortion to a local chalcopyrite coordination around the anions, explains also most of the observed optical bowing in semiconductor alloys.
151 citations
TL;DR: In this paper, a first-principles all-electron band-structure approach was used to show that the anomalous (g 50%) reduction in the band gaps of the chalcopyrite semiconductors relative to their II-VI isoelectronic analogs results both from a pure structural effect (the anion displacements reflecting the mismatch of classical elemental radii) and from a purely electronic effect, with a small coupling between the two factors.
Abstract: Using a first-principles all-electron band-structure approach, we show that the anomalous (g 50%) reduction in the band gaps of the ${A}^{\mathrm{I}}{B}^{\mathrm{III}}{C}_{2}^{\mathrm{VI}}$ chalcopyrite semiconductors relative to their II-VI isoelectronic analogs results both from a pure structural effect (the anion displacements reflecting the mismatch of classical elemental radii) and from a purely electronic effect ($p\ensuremath{-}d$ repulsion in the valence band), with a small coupling between the two factors.
145 citations
TL;DR: In this paper, a density-functional approach is proposed to directly calculate the ground-state energy of polyatomic systems with arbitrarily located nuclei and their accompanying electrons, which permits simultaneous relaxation of both the atomic geometries and the electronic charge densities.
Abstract: A simple formalism is presented, within the density-functional approach, which constitutes a powerful scheme for directly calculating the ground-state energy of systems with arbitrarily located nuclei and their accompanying electrons. The method permits simultaneous relaxation of both the atomic geometries and the electronic charge densities of polyatomic systems towards equilibrium. It circumvents the far less efficient indirect (consecutive) approach in which the equilibrium geometry is determined after calculation of energies on the Born-Oppenheimer surface.
65 citations
TL;DR: In this article, the electronic structure of neutral substitutional $3d$ transition-metal impurities in an infinite silicon host crystal has been calculated to within a high precision using pseudopotentials and the recently developed quasiband crystal field (QBCF) Green's-function method.
Abstract: The electronic structure of neutral substitutional $3d$ transition-metal impurities in an infinite silicon host crystal has been calculated for the first time. The calculation is carried out self-consistently in the local-density-functional formalism to within a high precision. We use nonlocal, first-principles pseudopotentials and the recently developed quasiband crystal-field (QBCF) Green's-function method. The elements of the electronic structure of this system are discussed in detail. The calculation reveals the chemical trends in the defect energies (gap states as well as resonances) for the impurities Zn, Cu, Ni, Co, Fe, Mn, Cr, V, and Ti, as well as the regularities in the density of states, wave functions, charge distributions, and screening potentials. For charged impurities, the model explains the remarkable occurrence of many charge states in the narrow-band-gap region through a new self-regulating mechanism analogous to the homeostasis control in biological systems.
52 citations
TL;DR: In this article, a selfconsistent one-electron model with broken symmetries (crystal orbitals are not constrained to be Bloch periodic) was proposed to describe core-ionization, core-exciton, and core-to-conduction-band transition energies in semiconductors.
Abstract: It is shown that in contrast to band theory, a self-consistent one-electron model with broken symmetries (crystal orbitals are not constrained to be Bloch periodic) provides a physical description of core-ionization, core-exciton, and core-to-conduction-band transition energies in semiconductors. Application to GaP shows that a hitherto unrecognized factor---the screening of the core-hole self-energy by the electron orbit---can explain many of the outstanding puzzles in core-hole spectra.
26 citations
TL;DR: In this paper, the origin of the Schottky barrier on the cleavage plane of III-V semiconductors is investigated using the Al/GaAs(110) system as a benchmark.
23 citations
TL;DR: In this paper, a precise selfconsistent calculation of the electronic structure of neutral substitutional 3D impurities in silicon within the local density formalism reveals striking chemical regularities, and the remarkable compression of the energy level ladder corresponding to different charged states in a narrow energy gap is shown to result from a special charge selfregulating mechanism, much like homeostasis in biology.
22 citations
TL;DR: In this paper, a first-principles calculation of the electronic structure of chalcogen impurities (0, S, and Se) in silicon was performed using the Green's-function method.
Abstract: We report the results of a first-principles calculation of the electronic structure of substitutional, unrelaxed, and neutral chalcogen impurities (0, S, and Se) in silicon. We have employed the recently developed quasi band crystal-field defect Green's-function method. We find that whereas atomistic models predict that the binding energies of donor levels in semiconductors increase with the ionization potential of the free impurity atoms, a special enhancement of the screening in the solid predicts, for chalcogen impurities in silicon, a reversal in this order. Our results are in excellent agreement with recently reported optical excitation data available for Si:S and Si:Se. We demonstrate that whereas oxygen shows the expected sp bonding to the host crystal, sulfur and selenium exhibit also significant d bonding by utilizing their virtual d states. We discuss the relevance of effective-mass — type calculations to chalcogen impurities in the light of our results.
17 citations
TL;DR: In this paper, the adatom states for different Al coverages of InP(110) by synchrotron-radiation photoemission were investigated, including ultralow coverages below 0.2 monolayer.
Abstract: We investigated the adatom states for different Al coverages of InP(110) by synchrotron‐radiation photoemission, including ultralow coverages below 0.2 monolayer. The adatom states below 0.1 monolayer and above ∼3 monolayer appear similar to the corresponding Al–adatom states on GaAs(110). In particular, the results for both systems appear consistent with the formation of Al clusters at 0.1–2 monolayer coverage, and the Fermi‐level pinning occurs when the cluster formation starts. However, the similarity between the two systems is limited at intermediate (0.1–2 monolayer) coverages. At those coverages we observe a new bonded state for Al on InP, which is not observed on GaAs. Our results emphasize, in general, the need to extend the experiments to ultralow coverages when studying the Schottky barrier formation process.
14 citations
TL;DR: In this article, it was shown that the local density formalism does not describe correctly the symmetry of the many-electron ground state of unrelaxed interstitial transition-atom impurities in silicon, but that a self-interaction correction to it produces the observed ground-state symmetries.
Abstract: It is shown that the local-density formalism does not describe correctly the symmetry of the many-electron ground state of unrelaxed interstitial transition-atom impurities in silicon, but that a self-interaction correction to it produces the observed ground-state symmetries
TL;DR: In this article, a special enhancement of the screening in the solid predicts, for chalcogen impurities in silicon, a reversal in this order, whereas atomistic models predict that binding energies of donor levels in semiconductors increase with the ionization potential of the free impurity atoms.
Abstract: Whereas atomistic models predict that binding energies of donor levels in semiconductors increase with the ionization potential of the free impurity atoms, we find that a special enhancement of the screening in the solid predicts, for chalcogen impurities in silicon, a reversal in this order
TL;DR: In this paper, a self-consistent calculation within the local density approximation for all the substitutional 3D transition atom (TA) impurities in an extended silicon host crystal using the quasi band Green's function method is presented.
Abstract: We report the results of a self-consistent calculation within the local density approximation for all the substitutional 3d transition atom (TA) impurities in an extended silicon host crystal using the quasi band Green's function method. Chemical trends in the gap state energies and 3d-line resonances are discussed as well as trends in the effective electronic configuration of TA impurities. An explanation for the remarkable property that many different charged states of TA impurities exist in the narrow band gap, despite the fact that the corresponding ionized states of the free TA span a range of ∼ 60 eV, is proposed.
TL;DR: D Daniels et al. as mentioned in this paper presented a QS531 Reference LSE-ARTICLE-1983-003 Record created on 2006-10-03, modified on 2016-08-08.
Abstract: Note: Solar energy res inst,golden,co 80401. univ colorado,dept phys,boulder,co 80309. Daniels, rr, univ wisconsin,dept phys,madison,wi 53706.ISI Document Delivery No.: QS531 Reference LSE-ARTICLE-1983-003 Record created on 2006-10-03, modified on 2016-08-08