A brief review of the theoretical state of the art in the field of semiconductor interfaces is presented. Itis shown that the important factor controlling the different semiconductor barrier heights is the densityof states associated with the semiconductor dangling-bonds. Passivated semiconductor surfaces presentsaturated dangling-bonds and have modified barrier heights. Results for hydrogen-passivated GaAs(11O)-surfaces are presented; it is shown that the Schottky-barrier height formed by the deposition of a K-layeris sustantially changed by the hydrogen-passivation. 1 INTRODUCTION Interfaces of crystalline materials are at the heart of different devices, and their understanding is basic toan appropriate design of many microelectronic systems. In this regard, semiconductors and their interfaceswith other semiconductors or metals have received the major attention1 , and we shall concentrate ourdiscussion in this paper on analyzing their basic electronic properties and their relation to the formationof different barriers.There are, basically, two kinds of semiconductor contacts: metal- semiconductor2'3 and semiconductor-semiconductor interfaces4. A great deal of the recent research in this field has been addressed to under-standing how their different barrier heights depend on the properties of the crystals forming the contact5.Fig.1 shows the main parameters defining each barrier: (a) for a metal semiconductor interface,

Interfaces in crystalline materials

Understanding the mechanisms which determine the band offsets and Schottky barriers at semiconductor contacts and engineering them for specific device applications are important theoretical and technological challenges. In this review, we present a theoretical approach to the band-line-up problem and discuss its application to prototypical systems. The emphasis is on ab initio computations and on theoretical models derived from first-principles numerical experiments. An approach based on linear-response-theory concepts allows a general description of the band alignment for various classes of semiconductor contacts and predicts the effects of various bulk and interfacial perturbations on the band discontinuities.

http://iopscience.iop.org/article/10.1088/0022-3727/31/11/002/pdf

Band engineering at interfaces : Theory and numerical experiments

Metal-semiconductor contacts: electronic properties

L’obiettivo di questo lavoro e duplice. Da un lato si procede a verificare la rilevanza dello spazio nella determinazione dei salari; dall’altro mira a rilevare la presenza e la presenza di un gap produttivo tra i lavoratori del Nord e quelli del Mezzogiorno d’Italia. Partendo dal modello della Nuova Geografia Economica di Helpman (1998) e tenendo conto di una serie di modifiche, in linea con Mion e Naticchioni (2004) e da Brakman et al. (2005) procediamo a verificare empiricamente la rilevanza della densita occupazionale e l’esistenza di un gap produttivo nella funzione dei salari. L’analisi empirica e svolta su un panel di dati relativo ai lavoratori dipendenti. Gli strumenti econometrici utilizzati sono quelli classici dell’analisi per dati panel statici (fixed e random effect) con l’aggiunta di strumenti dell’econometria spaziale per dati panel (Elhorst 2003) al fine di verificare la rilevanza dello spazio nella determinazione dei salari dei lavoratori dipendenti. In aggiunta stime con GMM sono implementate al fine di testare la sospettata presenza di endogenita in alcuni regressori, quali la densita occupazionale e il potenziale di mercato. JEL: C15, C21, F12, J6, J21, R12

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Universit` a degli Studi di Napoli

Energetics of metal/ceramic interfaces, metal-semiconductor Schottky contacts, and their relationship

1. Preliminary Remarks.- 2. Conceptual Models.- 2.1 Schottky-Mott Rule.- 2.2 Interface States.- 2.3 Continuum of Metal-Induced Gap States.- 2.4 MIGS-plus-Defects Model.- 2.5 Charge Transfer at Interface.- 3. Computational Results.- 4. Experimental Data.- 4.1 Chemical Trend of the Slope Parameters.- 4.2 Correlations with Chemical Reactivity.- 4.3 Effective Work Function Model.- 4.4 MIGS-plus-Defect Model.- 4.5 Direct Observation of the Continuum of MIG States.- 5. Surface-Science Approach to Schottky Contacts.- 5.1 Growth Modes of Nonreactive Metals on Semiconductors.- 5.2 Surface Band-Bending as a Function of Metal Coverage.- 5.3 Unified Defect Model.- 6. Concluding Remarks.- References:.- Reprinted Articles.- Additional Reference.- Reprinted Articles.- Ueber die Stromleitung durch Schwefelmetalle, Pogg. Ann. (1874).- Zum Mechanismus der Richtwirkung in Kupferoxydulgleichrichtern, Physik. Z. (1929).- Halbleitertheorie der Sperrschicht, Naturwissenschaften (1938).- Note on the Contact between a Metal and an Insulator or Semiconductor, Proc. Camb. Phil. Soc. (1938).- Abweichungen vom Ohmschen Gesetz in Halbleitern, Physik. Z. (1940).- Surface States and Rectification at a Metal Semiconductor Contact, Phys. Rev. (1947).- Surface States and Barrier Height of Metal Semiconductor Systems, J. Appl. Phys. (1965).- Theory of Surface States, Phys. Rev. (1965).- Fundamental Transition in the Electronic Nature of Solids, Phys. Rev. Lett. (1969).- Density of States and Barrier Height of Metal-Si Contacts, J. Phys. C: Solid State Physics (1971).- Metal-semiconductor Junctions for (110) Surfaces of Zinc-blende Compunds, Phys. Rev. B (1976).- Electronic Structure of a Metal Semiconductor Interface, Phys. Rev. B (1976).- Ionicity and the Theory of Schottky Barriers, Phys. Rev. B (1977).- Chemical Trends in Metal-semiconductor Barrier Heights, Phys. Rev. B (1978).- Transition in Schottky Barrier Formation with Chemical Reactivity, Phys. Rev. Lett. (1978).- New and Unified Model for Schottky Barrier and III-V Insulator Interface States Formation, J. Vac. Sci. Technol. (1979).- Schottky Barriers: An Effective Work Function Model, AppL Phys. Lett. (1981).- The Foramtion of the Schottky Barrier at the V/Si Interface, J. Vac. Sci. Technol. (1982).- Formation of Ultrathin Single- Crystal Silicide Films on Si: Surface and Interfacial Stabilization of Si-NiSi2Epitaxial Strucutures, Phys. Rev. Lett. (1983).- Schottky Barrier Heights and the Continuum of Gap States, Phys. Rev. Lett. (1984).- Schottky Barrier Formation at Single-Crystal Metal Semiconductor Interfaces, Phys. Rev. Lett. (1984).- Reflection High-energy Electron Diffraction Study of the Growth of In on GaAs (110) at Different Temperatures, J. Vac. Sci. Tecnol. B (1986).- Direct Variation of Metal-GaAs Schottky Barrier Height by the Influence of Interface S, Se and Te, AppL Phys. Lett. (1985).- Interface Potential Changes and Scottky Barriers, Phys. Rev. B (1985).- Ruthenium-Induced Surface Staes of n-GaAs Surfaces, J. Vac. Sci. Technol. B. (1986).- Metallization and Scottky Barrier Formation, Phys. Rev. B (1986).- On the Present Understanding of Schottky Contacts , Festkorperprobleme (1986).- Role of Virtual Gap States and Defects in Metal Semiconductor Contacts Phys. Rev. Lett. (1987).- Initial Stages of Schottky Barrier Formation: Temperature Effects, J. Vac. Sci. Technol. B (1987).- Kinetics Study of Initial Stage Band Bending at Metal GaAs (110) Interfaces, J. Vac. Sci. Technol. B (1987).- The Schottky Contact in a Xe/Metal Interface Probed by Inverse Photoemission, Europhys. Lett. (1987).- Origin of the Excess Capacitance at Intimate Schottky Contacts, Phys. Rev. Lett. (1988).- Correlation between EfPinning and Development Metallic Character in Ag Overlayers on GaAs (110), Phys. Rev. Lett. (1988).- Direct Investigation of Subsurface Interface Electronic Structure by Ballistic-Electron-Emission Microscopy, Phys. Rev. Lett. (1988).- Chemical Trends in Schottky Barriers: Charge Transfer into Adsorbate Induced Gap States and Defects, Phys. Rev. B (1988).- The Advanced Unified Defect Model for Schottky Barrier Formation, J. Vac. Sci. Technol. B (1988).- Screening and Derealization Effects in Schottky Barrier Formation, J. Vac. Sci. Technol. B (1988).- Tight-Binding Model of Surface Donor-States Induced by Metal Adatoms on GaAs (110) Surfaces, Europhys. Lett. (1988).- Switching of Band Bending at the Nonreactive CsOx/GaAs (110) Interface, Phys. Rev. Lett. (1989).- Metallicity and Gap States in Tunneling to Fe Clusters on GaAs (110), Phys. Rev. Lett. (1989).

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Winfried Mönch

Papers

Electronic Structure of Metal-Semiconductor Contacts