Search query: Unified disorder induced gap state model for insulator–semiconductor and metal– semiconductor interfaces

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abstract: The energy location for the interface state density Nss minimum of the insulator semiconductor (I S) interface and the Fermi level pinning position at the metal semiconductor (M S) interface are shown to coincide and to lie at the same position of 5.0 eV from the vacuum level for major tetrahedral semiconductors. Neither the unified defect model nor the metal induced gap state model can explain the novel striking correlation between the I S and M S interfaces. The correlation as well as the observed peculiar photoionization behavior of the I S interface are explained by the novel unified disorder induced gap state (DIGS) model where DIGS pin or restrict the movement of the surface Fermi level. The above characteristic energy, EHO, is shown to be the Fermi energy of the DIGS spectrum which is given by the hybrid orbital energy of the sp3 bond of the host. The DIGS model explains remarkably well the behavior of the M S interface formed on the bare or oxide covered semiconductor surface as well as the variou.
author_names: Hideki Hasegawa

Hideo Ohno
title: Unified disorder induced gap state model for insulator semiconductor and metal semiconductor interfaces
year: 1986

abstract: Compound semiconductor metal insulator semiconductor (MIS) capacitance voltage (C V) curves are simulated on a computer, assuming the presence of a disorder induced gap state (DIGS) continuum near the interface in which bonding and antibonding states are distributed both in space and in energy around a particular charge neutrality point, EHO A program based on Shockley Read Hall statistics is developed and applied to simulate a set of experimental MIS C V curves measured on Al2 O3 /native oxide/InP MIS capacitors. By assuming a particular type of energy and spatial distribution of DIGS continuum and a suitable single set of dynamic parameters, the simulation can completely and self consistently reproduce the experimental MIS C V curves with complex hysteresis behavior, which varies with the bias amplitude and swing speed. The excellent agreement between theory and experiment supports the DIGS model. The danger involved in simply applying Terman's method to determine an Nss distribution is pointed out. A.
author_names: Li He

Hideki Hasegawa

Takayuki Sawada

Hideo Ohno
title: A self consistent computer simulation of compound semiconductor metal insulator semiconductor C V curves based on the disorder induced gap state model
year: 1988

abstract: The origin of the anomalous frequency dispersion in accumulation capacitance of metal insulator semiconductor devices on InGaAs and InP substrates is investigated using modeling, electrical characterization, and chemical characterization. A comparison of the border trap model and the disorder induced gap state model for frequency dispersion is performed. The fitting of both models to experimental data indicate that the defects responsible for the measured dispersion are within approximately 0.8 nm of the surface of the crystalline semiconductor. The correlation between the spectroscopically detected bonding states at the dielectric/III V interface, the interfacial defect density determined using capacitance voltage, and modeled capacitance voltage response strongly suggests that these defects are associated with the disruption of the III V atomic bonding and not border traps associated with bonding defects within the high k dielectric.
author_names: Rohit Galatage

Dmitry Zhernokletov

Hong Dong

Barry Brennan

Christopher L Hinkle

Robert M Wallace

Eric M Vogel
title: Accumulation capacitance frequency dispersion of III V metal insulator semiconductor devices due to disorder induced gap states
year: 2014

abstract: Abstract Based on the recently proposed disorder induced gap state (DIGS) model for interface states, the charge discharge dynamics of interface state continuum at insulator semiconductor (I S) interfaces are theoretically analyzed and compared with the experiments on InP and InGaAs MIS structures. The concept occupation boundary used in the analysis clarifies the physics involved and simplifies the simulation of complex processes. By assuming a particular type of DIGS distribution in energy and in space, the observed complex hysteresis behavior of dispersion of MIS capacitance in MIS C V curves as well as the current drift behavior of MISFET's are completely reproduced on computer, offering a unified understanding of a wide variety of phenomena associated with I S interfaces.
author_names: Li He

Hideki Hasegawa

Jikui Luo

Hideo Ohno
title: Charge discharge dynamics of disorder induced gap state continuum at compound semiconductor insulator interfaces
year: 1988

abstract: It is commonly accepted that interface states at the passivation surface of AlGaN/GaN heterostructures play an important role in the formation of the 2DEG density. Several interface state models are cited throughout literature, some with discrete levels, others with different kinds of distributions, or a combination of both. The purpose of this article is to compare the existing interface state models with both direct and indirect measurements of these interface states from literature (e.g. through the hysteresis of transfer characteristics of Metal Insulator Semiconductor High Electron Mobility Transistors (MISHEMTs) employing such an interface in the gate region) and Technology Computer Aided Design (TCAD) simulations of 2DEG densities as a function of the AlGaN thickness. The discrepancies between those measurements and TCAD simulations (also those commonly found in literature) are discussed. Then, an alternative model inspired by the Disorder Induced Gap State model for compound semiconductors is proposed. It is shown that defining a deep border trap inside the insulator can solve these discrepancies and that this alternative model can explain the origin of the two dimensional electron gas in combination with a high quality interface that, by definition, has a low interface state density.
author_names: Benoit Bakeroot

Shuzhen You

T -L Wu

Jie Hu

Marleen Van Hove

Brice De Jaeger

Karen Geens

Steve Stoffels

Stefaan Decoutere
title: On the origin of the two dimensional electron gas at AlGaN/GaN heterojunctions and its influence on recessed gate metal insulator semiconductor high electron mobility transistors
year: 2014

abstract: We have obtained Al/SiNx:H/Si and Al/SiNx:H/InP Metal Insulator Semiconductor devices by directly depositing silicon nitride thin films on silicon and indium phosphide wafers by the Electron Cyclotron Resonance Plasma method at 200 degrees C. The electrical properties of the structures were first analyzed by Capacitance Voltage measurements and Deep Level Transient Spectroscopy (DLTS) Some discrepancies in the absolute value of the interface trap densities were found. Later on, Admittance measurements were carried out and room and low temperature conductance transients in the silicon nitride/semiconductor interfaces were found. The shape of the conductance transients varied with the frequency and temperature at which they were obtained. This behavior, as well as the previously mentioned discrepancies, are explained in terms of a disorder induced gap state continuum model for the interfacial defects. A perfect agreement between experiment and theory is obtained proving the validity of the model.
author_names: Salvador Duenas

Ramon Javier Pelaez

E Castan

Juan Barbolla

I Martil

G Gonzalez-Diaz
title: Conductance Transients Study of Slow Traps in Al/SiN x :H/Si and Al/SiN x :H/InP Metal Insulator Semiconductor Structures
year: 1997

abstract: Room temperature conductance transients in the SiNx:H/Si interface are reported. Silicon nitride thin films were directly deposited on silicon by the low temperature electron cyclotron resonance plasma method. The shape of the conductance transients varies with the frequency at which they are obtained. This behavior is explained in terms of a disorder induced gap state continuum model for the interfacial defects. A perfect agreement between experiment and theory is obtained proving the validity of the model.
author_names: Salvador Duenas

Ramon Javier Pelaez

E Castan

Ruth Pinacho

Luis Quintanilla

Juan Barbolla

I Martil

G Gonzalez-Diaz
title: Experimental observation of conductance transients in Al/SiNx:H/Si metal insulator semiconductor structures
year: 1997

abstract: Electrical transport through molecular monolayers being very sensitive to disorder effects, admittance and current density characteristics of Hg C12H25 n Si junctions incorporating covalently bonded n alkyl molecular layers, were investigated at low temperature (150 300 K) in the as grafted state and after ageing at the ambient. This comparison reveals local oxidation effects both at the submicron scale in the effective barrier height distribution and at the molecular scale in the dipolar relaxation. In the bias range dominated by thermionic emission and modified by the tunnel barrier attenuation, where is the thickness of the molecular tunnel barrier and is the inverse attenuation length at zero applied bias, some excess current is attributed to a distribution of low barrier height patches. Complementary methods are used to analyze the current density J(V, T) characteristics of Metal Insulator Semiconductor tunnel diodes. Assuming a Gaussian distribution of barrier heights centered at provides an analytical expression of the effective barrier height, this allows fitting of the distribution standard deviation and tunnel parameter over a wide temperature range. In a more realistic modeling including the voltage dependence of barrier height and circular patch area, the so called "pinch off" effect is described by a distribution of parameter which combines interface potential modulation and patch area variations. An arbitrary distribution of values, fitted to low temperature J(V) data, is equally well described by Gaussian or exponential functions. Ageing in air also increases the interface oxidation of Si substrate and affects the density of localized states near mid gap, which typically rises to the high 1011 eV 1.cm 2 range, as compared with 1011 eV 1.cm 2 in the as grafted state. The bias independent relaxation observed near 1 kHz at low temperature may be attributed either to dipoles in the alkyl chain induced by the strong permanent dipoles of interface silicon oxide or to a local relaxation of water molecules trapped at the OML silicon interface. The respective roles of SiO2 formation and water physisorption on the decrease of patch barrier height are also discussed.
author_names: Alain-Bruno Fadjie-Djomkam

Soraya Ababou-Girard

Christian Godet
title: Barrier height distribution and dipolar relaxation in metal insulator semiconductor junctions with molecular insulator: Ageing effects
year: 2012

abstract: 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)
author_names: Winfried Monch
title: Electronic Structure of Metal Semiconductor Contacts
year: 1990

abstract: for Talks 2 Monday, January 7, 2019 (Day 1) 09:20 09:50 Topological Superfluid for 1D Spin 1 Bosons and Its Continuous Phase Transition Prof. Xiao Gang Wen Massachusetts Institute of Technology Spin 1 bosons on a 1 dimensional chain, with anti ferromagnetic spin interaction between neighboring bosons, may form a spin 1 boson condensed state that contains both gapless charge and spin excitations. We argue that the spin 1 boson condensed state is unstable, and will become one of two superfluids by opening a spin gap. One superfluid must have spin 1 ground state on a ring if it contains an odd number of bosons and has no degenerate states at the chain end. The other superfluid has spin 0 ground state on a ring for any numbers of bosons and has a spin 1/2 degeneracy at the chain end. The two superfluids have the same symmetry and only differ by a spin SO(3) symmetry protected topological order. Although Landau theory forbids a continuous phase transition between two phases with the same symmetry, the phase transition between the two superfluids can be generically continuous, which is described by a conformal field theory (CFT) Such a CFT has a spin fractionalization: a spin1 excitation can decay into a spin 1/2 right mover and a spin 1/2 left mover. Abstract for Talks 3for Talks 3 Monday, January 7, 2019 (Day 1) 09:50 10:20 Superconductivity in Sr2RuO4: Theory vs Experiments Prof. Qiang Hua Wang Nanjing University We use functional renormalization group method to study a three orbital model for superconducting Sr2RuO4. The pairing symmetry is found to be chiral p wave, but the atomic spin orbit coupling induces near nodes for quasiparticle excitations. The theory is compared to a variety of experimental data, with excellent agreements. In particular, the theory explains a major experimental puzzle between d wave like feature observed in thermal experiments and the chiral p wave triplet pairing revealed in nuclear magnetic resonance and Kerr effect. Other co authors: Wan Sheng Wang, Ningbo University, China; Fu Chun Zhang, University of Chinese Academy of Science, China Abstract for Talks 4for Talks 4 Monday, January 7, 2019 (Day 1) 10:20 10:50 Chiral Magnetic Effect and Collective Modes in Topological Semimetals Prof. Xi Dai Hong Kong University of Science and Technology Quasi particles and collective modes are two fundamental aspects that characterize a quantum mater in additional to its ground state features. For example, the low energy physics for Fermi liquid phase in He III was featured not only by Fermionic quasi particles near the chemical potential, but also by fruitful collective modes in the long wave length limit, including several different sound waves that can propagate through it under different circumstances. On the other hand, it is very difficult for sound waves to be carried by the electron liquid in the ordinary metals, due to the fact that long range Coulomb interaction among electrons will generate plasmon gap for ordinary electron density waves and thus prohibits the propagation of sound waves through the electron liquid. In the present paper, we propose a unique type of acoustic collective modes formed by Weyl fermions under the magnetic field, which is called chiral zero sound (CZS) The CZS only exists and propagates along an external magnetic field for Weyl semi metal systems containing multiple pairs of Weyl points. The sound velocity of CZS is proportional to the field strength in the weak field limit, whereas oscillates dramatically in the strong field limit generating completely new mechanism for quantum oscillations through the dynamics of neutral Bosonic excitation, which may manifest itself in the thermal conductivity measurements under magnetic field. Abstract for Talks 5for Talks 5 Monday, January 7, 2019 (Day 1) 11:30 12:00 Daniel Tsui Fellowship Award Presentation Emergent Quantum Criticality in Spin 1 Magnets and Some Thoughts on Thermal Hall Transports Dr. Gang Chen The University of Hong Kong Abstract for Talks 6for Talks 6 Monday, January 7, 2019 (Day 1) 14:00 14:30 Resonantly Enhanced Moire Superlattice Coupling in Transition Metal Dichalcogenide Bilayers with Almost Matching Band Edges Prof. Vladimir Fal'ko National Graphene Institute, UK Atomically thin layers of two dimensional materials can be assembled in vertical stacks held together by relatively weak van der Waals forces, allowing for coupling between monolayer crystals with incommensurate lattices and arbitrary mutual rotation. A profound consequence of using these degrees of freedom is the emergence of a periodicity in the local atomic registry of the constituent crystal structures, known as a moire superlattice. Here, we discuss how moire superlattice effects on the electronic properties of almost aligned MoSe2/WS2 and MoTe2/MoSe2 heterobilayers get enhanced by resonant hybridization of conduction band states in different layers, promoted by alignment of their band edges [1] In particular, we find that in semiconducting heterostructures built of incommensurate MoSe2 and WS2 monolayers, A exciton undergoes an almost resonant interlayer hybridisation, resulting in the enhancement of the moire superlattice effects, as an electron in the exciton explores efficiently the local arrangement of atoms in the two layer. MoSe2 and WS2 are specifically chosen for the near degeneracy of their conduction band edges to promote the hybridisation of intraand interlayer excitons, which manifests itself in photoluminescence through a pronounced exciton energy shift as a periodic function of the interlayer rotation angle. This occurs as hybridised excitons (hX) are formed by holes residing in MoSe2 bound to a twist dependent superposition of electron states in the adjacent monolayers. For heterostructures with almost aligned pairs of monolayer crystals, resonant mixing of the electron states leads to pronounced effects of the heterostructure's geometrical moire pattern on the hX dispersion and optical spectrum, including the appearance of new lines in their optical absorption spectra that correspond to the electron photon umklapp processes. We also show that similar resonant hybridization is possible for B excitons in some TMD heterostructures, and that they should naturally appear in twisted homobilayers of various transition metal dichalcogenides. [1] D.A. Ruiz Tijerina and V.I. Fal'ko, arXiv:1809.09257 Other co authors: D.A. Ruiz Tijerina, National Graphene Institute, University of Manchester, Booth St E, M13 9PL, Manchester, UK Abstract for Talks 7for Talks 7 Monday, January 7, 2019 (Day 1) 14:30 15:00 Probing and Tuning Interlayer Interactions to Control Electronic and Photonic Properties of 2D Heterostructures Prof. Chih Kang Shih The University of Texas at Austin Atomically thin, single crystalline 2D electronic materials have recently emerged, offering a remarkably wide range of building blocks of nanostructures, ranging from metals (e.g. graphene) large gap insulators (BN) to semiconductors (transition metal dichalcogenides and black phosphorous) One key advantage of these van der Waals materials lies in the flexibility of stacking different types of materials to form heterostructures, providing a design platform for achieving novel device functionality. In vdW hetero bilayers, the interface encompasses the whole heterostructure and interlalyer interactions become the controlling parameter for the electronic structure. In this talk I will first discuss directly probing the inter layer interactions through the "lens" of moire patterns using scanning tunneling microscopy and spectroscopy (STM/S) I will show that the interlayer coupling is strongly dependent on the interatomic alignment of the constituent layers. Moreover, as a consequence of moire pattern formation, the energy band structure of the hetero bilayer also shows lateral modulation, forming a 2D electronic superlattice. The moire pattern "lens" also provides us with a means to measure the 2D strain tensor with high precision and high spatial resolution. In addition, the strain profile shows a direct correlation with the band gap modification. As the periodic potential modulation also provides lateral confinement for excitons, an intriguing scenario occurs the 2D lateral superlattices also form 2D exciton quantum dot arrays. Recent reports of ultra sharp atomic like spectra provide a direct confirmation of such a scenario. Finally, I will add another control knob and show evidence for valley spin mediated interlayer couplings, and their effect on excitonic states of the hetero bilayer. Abstract for Talks 8for Talks 8 Monday, January 7, 2019 (Day 1) 15:00 15:30 Low energy Moire Band Formed by Dirac Zero Modes in Twisted Bilayer Graphene Dr. Long Zhang University of Chinese Academy of Sciences An unconventional insulating phase and a superconducting phase were recently discovered in the twisted bilayer graphene [Y. Cao et al, Nature 556, 80; 556, 43 (2018) but the relevant low energy electronic states have not been clearly identified yet. In this work, I show that the interlayer hopping induces a spatially modulated Dirac mass term in the continuum Hamiltonian, and leads to a low energy band formed by Dirac zero modes in the moire superlattice. This moire band becomes extremely flat and thus strongly correlated when the Dirac velocity vanishes approaching the magic angle, and enters a quantum disordered Mott insulating phase at 1/4 and 3/4 filling, i.e. 2 excess electrons per moire supercell, which may account for the insulating phase discovered in experiments. This model should be a good starting point for studying the exotic superconducting phase in slightly doped twisted bilayer graphene. Abstract for Talks 9for Talks 9 Monday, January 7, 2019 (Day 1) 16:00 16:30 Hidden SU(2) Symmetries, the Symmetry Hierarchy and the Emergent Eight Fold Way in Spin 1 Quantum Magnets Prof. Yi Zhou Zhejiang University The largest allowed symmetry in a
author_names: Xiao-Gang Wen

Qiang Wang

Wan-Sheng Wang
title: Hong Kong Forum of Physics 2018: Recent Progress in Quantum Matter Theories and Experiments
year: 2019