Showing papers by "Alex Zunger published in 1986"
TL;DR: In this article, the authors present a review on the recent developments vis a vis the new experimental methodologies and the classical phenomenological approaches used earlier to understand deep 3D impurities.
Abstract: Publisher Summary The chapter presents a discussion on electronic structure of three-dimensional (3d) transition-atom impurities in semiconductors. The effects of 3d impurities in semiconductors have preoccupied the field since the invention of the transistor. Reliable experimental data for germanium and silicon became available quite early. The chapter presents an in-depth review of the present status of the field. This review contains a most careful and detailed exposition of various aspects of the subject, presented, as the author states using “the combined points of view of theoretical solid-state physics, semiconductor physics, and classical inorganic chemistry.” The chapter discusses the great progress that has been made. The chapter presents a review on the recent developments vis a vis the new experimental methodologies and the classical phenomenological approaches used earlier to understand deep 3d impurities. The author attempts to present a coherent picture of the understanding of isolated 3d impurities in cubic semiconductors from the combined points of view of theoretical solid-state physics, semiconductor physics, and classical inorganic chemistry.
195 citations
TL;DR: A theoretical analysis of optical bowing observed in isovalent semiconductor systems for ordered 50%-50% alloys in the CuAu-I structure predicts correct bowing parameters and chemical trends, yet suggests a physical model which is altogether different from the virtual-crystal model.
Abstract: Alloys of zinc chalcogenides exhibit both some of the smallest (for $\mathrm{Zn}{\mathrm{S}}_{x}{\mathrm{Se}}_{1\ensuremath{-}x}$) and the largest (for $\mathrm{Zn}{\mathrm{S}}_{x}{\mathrm{Te}}_{1\ensuremath{-}x}$) optical bowing observed in isovalent semiconductor systems. A theoretical analysis of this effect, by use of self-consistent band-structure techniques for ordered 50%-50% alloys in the CuAu-I structure, predicts correct bowing parameters and chemical trends, yet suggests a physical model which is altogether different from the virtual-crystal model.
177 citations
TL;DR: Using first-principles self-consistent total-energy calculations for unconstrained and epitaxially confined models of Si-C and Si-Ge alloys, the general classes of stability of ordered phases of semiconductor alloys are studied.
Abstract: Using first-principles self-consistent total-energy calculations for unconstrained and epitaxially confined models of Si-C and Si-Ge alloys we study the general classes of stability of ordered phases of semiconductor alloys. The unusual ordering observed in SiGe grown on a Si substrate is explained.
139 citations
TL;DR: Calcul de la structure electronique des phases cubiques ordonnees α, β et δ de LiZnAs dans la meme structure, d'une cohesion superieure par rapport a l'analogue III-V (GaAs) et de comportement metallique (forme γ) ou semiconducteur (α et β).
Abstract: The first electronic structure calculation of the ordered \ensuremath{\alpha}, \ensuremath{\beta}, and \ensuremath{\gamma} cubic phases of an ``interstitially filled tetrahedral compound'' ${\mathrm{A}}^{\mathrm{I}{\mathrm{B}}^{\mathrm{II}{\mathrm{C}}^{\mathrm{V}}}}$ (where the ${\mathrm{B}}^{\mathrm{II}}$ and ${\mathrm{C}}^{\mathrm{V}}$ atoms occupy the normal zincblende sites and ${\mathrm{A}}^{\mathrm{I}}$ occupies one of the empty zincblende tetrahedral interstitial sites) reveals strongly covalent (${\mathrm{B}}^{\mathrm{II}\mathit{\ensuremath{-}}{\mathrm{C}}^{\mathrm{V}}}$) and strongly ionic (${\mathrm{A}}^{\mathrm{I}\mathit{\ensuremath{-}}{\mathrm{C}}^{\mathrm{V}}}$) bonds in the same structure, uperior cohesion relative to the III-V analog (GaAs), and semiconducting (\ensuremath{\alpha} and \ensuremath{\beta} forms) as well as metallic (\ensuremath{\gamma}-form) behavior.
82 citations
TL;DR: This work model the structural, magnetic, and electronic properties of such a hitherto unknown zinc-blende-like MnTe phase through spin-polarized total-energy calculations, and report its unusual properties in both ferromagnetic and antiferromagnetic spin ordering.
Abstract: While MnTe has the stable NiAs structure with a direct band gap of 1.30 eV and a Mn-Te bond length of 2.92 \AA{}, extrapolation of the data for the zinc-blende alloy ${\mathrm{Cd}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{Te}$ to $x=1$ suggests an alloy-stabilized MnTe phase with very different properties: a band gap of \ensuremath{\sim}3 eV and a Mn-Te bond length of 2.73 \AA{}. We model the structural, magnetic, and electronic properties of such a hitherto unknown zinc-blende-like MnTe phase through spin-polarized total-energy calculations, and report its unusual properties in both ferromagnetic and antiferromagnetic spin ordering.
51 citations
TL;DR: The central-cell potential ..delta..V-italic/sub CC/(r) carries the specific signature of each atom, distinguishing therefore members of a given class from each other.
Abstract: The perturbation potential which transmutes a homopolar column-IV diamondlike semiconductor into either a heteropolar zinc-blende-like III-V or II-VI compound or an antifluorite semiconductor can be thought of as consisting of a sum of two terms: (i) a long-range Coulomb dipole potential ..delta..V-italic/sub dip/(r) associated with the different valence of the atoms of the compound relative to the atoms in the diamondlike system, and (ii) the remaining, short-range and primarily repulsive core pseudopotential ..delta..V-italic/sub CC/(r) (a ''central-cell'' correction). Whereas ..delta..V-italic/sub dip/(r) is common to all members of a given structural class (e.g., all III-V or all II-VI compounds or all antifluorite silicides), defining thereby generic semiconductors, the central-cell potential ..delta..V-italic/sub CC/(r) carries the specific signature of each atom, distinguishing therefore members of a given class from each other.
47 citations
TL;DR: All 3d impurities observed to date in tetrahedral semiconductors have a high-spin ground state, in agreement with Hund's rule, and it is predicted that the as yet unobserved ground state of GaAs:V/sup 2 +/ is of the low-spin type.
Abstract: All 3d impurities observed to date in tetrahedral semiconductors have a high-spin ground state, in agreement with Hund's rule. Using first-principles self-consistent Green's-function calculations for substitutional GaAs:V within the local-spin-density formalism, we predict that the as yet unobserved ground state of GaAs:V/sup 2 +/ is of the low-spin type. The origin of this unusual ground state is explained.
34 citations
TL;DR: In this article, the stability of ordered semiconductor alloys has been studied, using total energy pseudopotential calculations, and the ordered alloys are found to be stabilized with respect to disordered alloys via reduction of the internal strain and by chemical interactions.
Abstract: The stability of ordered semiconductor alloys has been studied, using total energy pseudopotential calculations. The ordered alloys are found to be stabilized with respect to disordered alloys via reduction of the internal strain and by chemical interactions. The Si–C and Si–Ge systems are used as illustrations, finding that ordered Six Ge1−x should be a metastable alloy, in agreement with experimental observations.
26 citations
TL;DR: In this article, the availability of structural degrees of freedom in various ternary AnB4−nC4 adamantine semiconductors was shown to lead to their energetic stabilization when grown epitaxially, and the substrate strain preferentially stabilize one structure over another even when the two are equally stable (or unstable) in bulk form.
Abstract: It is shown how the availability of structural degrees of freedom in various ternary AnB4−nC4 adamantine semiconductors can lead to their energetic stabilization when grown epitaxially, and how the substrate strain can preferentially stabilize one structure over another even when the two are equally stable (or unstable) in bulk form.
23 citations
TL;DR: Using 30-year-old ideas on Fermi-energy- (epsilon-c/sub F/) induced stability enhancements in impure semiconductors, it follows that if two impurity sites with different electrical levels exist, one can expect to find a critical Epsilon-c-sub F//sup b/ within the band gap.
Abstract: Using 30-year-old ideas on Fermi-energy- (${\ensuremath{\varepsilon}}_{F}$) induced stability enhancements in impure semiconductors, it follows that if two impurity sites with different electrical levels exist, one can expect to find, inside the band gap, a critical Fermi energy ${\ensuremath{\varepsilon}}_{F}^{b}$ such that one site is stable for ${\ensuremath{\varepsilon}}_{F}g{\ensuremath{\varepsilon}}_{F}^{b}$ and the other for ${\ensuremath{\varepsilon}}_{F}l{\ensuremath{\varepsilon}}_{F}^{b}$. This bifurcation of the site-preference energies leads to general metastabilities, as demonstrated here for Si:Mg and Si:Be, using self-consistent local-density total-energy calculations.
10 citations
TL;DR: In this paper, the magnetism of interstitial 3D impurities in silicon was discussed, and a mechanism of covalent reduction of both the hyperfine coupling constant and the orbital angular momentum part of the g -values was proposed.
TL;DR: In this article, the authors performed spin-polarized, self-consistent local spin density total energy and band structure calculations for the prototype semimagnetic semiconductor alloy Cd1-xMnxTe.
Abstract: We have performed spin-polarized, self-consistent local spin density total energy and band structure calculations for the prototype semimagnetic semiconductor alloy Cd1-xMnxTe. Based on the calculated band structures and taking into account the many body effects of localized states, we propose a schematic energy level diagram to interpret the d→d*, p→d, and photoemission transitions in Cd1-xMnxTe.