scholarly journals Temperature dependent Band gap Correction model using tight-binding approach for UTB device simulations

2022 ◽  
Author(s):  
Nalin Vilochan Mishra ◽  
Ravi Solanki ◽  
Harshit Kansal ◽  
Aditya S Medury
Keyword(s):  
Band Structure ◽  
Band Gap ◽  
Tight Binding ◽  
Thin Body ◽  
Temperature Dependent ◽  
Minor Variation ◽  
Correction Model ◽  
Wide Range ◽  
Channel Thickness ◽  
Semi Empirical

<div>Ultra-thin body (UTB) devices are being used in many electronic applications operating over a wide range of temperatures. The electrostatics of these devices depends on the band structure of the channel material, which varies with temperature as well as channel thickness. The semi-empirical tight binding (TB) approach is widely used for calculating channel thickness dependent band structure of any material, at a particular temperature, where TB parameters are defined. For elementary semiconductors like Si, Ge and compound semiconductors like GaAs, these TB parameters are generally defined at only 0 K and 300 K. This limits the ability of the TB approach to simulate the electrostatics of these devices at any other intermediate temperatures.</div><div>In this work, we analyze the variation of band structure for Si, Ge and GaAs over different channel thicknesses at 0 K and 300 K (for which TB parameters are available), and show that the band curvature at the band minima has minor variation with temperature, whereas the change of band gap significantly affects the channel electrostatics. Based on this finding, we propose an approach to simulate the electrostatics of UTB devices, at any temperature between 0 K and 300 K, using TB parameters defined at 0 K, along with a suitable channel thickness and temperature dependent band gap correction. </div>

scholarly journals Temperature dependent Band gap Correction model using tight-binding approach for UTB device simulations

2022 ◽  
Author(s):  
Nalin Vilochan Mishra ◽  
Ravi Solanki ◽  
Harshit Kansal ◽  
Aditya S Medury
Keyword(s):  
Band Structure ◽  
Band Gap ◽  
Tight Binding ◽  
Thin Body ◽  
Temperature Dependent ◽  
Minor Variation ◽  
Correction Model ◽  
Wide Range ◽  
Channel Thickness ◽  
Semi Empirical

<div>Ultra-thin body (UTB) devices are being used in many electronic applications operating over a wide range of temperatures. The electrostatics of these devices depends on the band structure of the channel material, which varies with temperature as well as channel thickness. The semi-empirical tight binding (TB) approach is widely used for calculating channel thickness dependent band structure of any material, at a particular temperature, where TB parameters are defined. For elementary semiconductors like Si, Ge and compound semiconductors like GaAs, these TB parameters are generally defined at only 0 K and 300 K. This limits the ability of the TB approach to simulate the electrostatics of these devices at any other intermediate temperatures.</div><div>In this work, we analyze the variation of band structure for Si, Ge and GaAs over different channel thicknesses at 0 K and 300 K (for which TB parameters are available), and show that the band curvature at the band minima has minor variation with temperature, whereas the change of band gap significantly affects the channel electrostatics. Based on this finding, we propose an approach to simulate the electrostatics of UTB devices, at any temperature between 0 K and 300 K, using TB parameters defined at 0 K, along with a suitable channel thickness and temperature dependent band gap correction. </div>

scholarly journals Reduced k-points based computationally efficient band structure approach for UTB device simulation

2021 ◽  
Author(s):  
Ravi Solanki ◽  
Nalin Vilochan Mishra ◽  
Aditya S Medury
Keyword(s):  
Band Structure ◽  
Density Functional ◽  
Tight Binding ◽  
Computational Time ◽  
Thin Body ◽  
Computationally Efficient ◽  
Wide Range ◽  
Full Band ◽  
Consistent Solution ◽  
Full Band Structure

The accurate calculation of channel electrostatics parameters, such as charge density and potential, in ultra-thin body (UTB) devices requires self-consistent solution of the Poisson’s equation and the full band structure, which is channel material and thickness dependent. For cubic crystals like silicon, the semi-empirical sp3d5s* tight-binding (TB) model is preferred in device simulations, over the density functional theory, to obtain the full band structure because of being computationally less intensive and equally accurate. However, the computational time of the TB model scales non-linearly with the channel thickness and becomes cumbersome for silicon, beyond 5 nm, primarily because of the increasing size of the TB hamiltonian that needs to be solved over the entire k-space, in the irreducible Brillouin zone. In this work, we precisely identify those k-points corresponding to the energies close to the band minima, where the Fermi-Dirac probability significantly affects electrostatics parameters. This enables us to demonstrate a computationally efficient approach based on solving the hamiltonian only on those reduced number of k-points. The rigorous benchmarking of the channel electrostatics parameters obtained from this approach is performed with results from accurate full band structure simulations showing excellent agreement over a wide range of channel thicknesses, oxide thicknesses, device temperatures and different channel orientations. By showing that the approach presented in this work is computationally efficient, besides being accurate, regardless of the number of atomic layers, we demonstrate its applicability for simulating UTB devices.

scholarly journals Reduced k-points based computationally efficient band structure approach for UTB device simulation

2021 ◽  
Author(s):  
Ravi Solanki ◽  
Nalin Vilochan Mishra ◽  
Aditya S Medury
Keyword(s):  
Band Structure ◽  
Density Functional ◽  
Tight Binding ◽  
Computational Time ◽  
Thin Body ◽  
Computationally Efficient ◽  
Wide Range ◽  
Full Band ◽  
Consistent Solution ◽  
Full Band Structure

The accurate calculation of channel electrostatics parameters, such as charge density and potential, in ultra-thin body (UTB) devices requires self-consistent solution of the Poisson’s equation and the full band structure, which is channel material and thickness dependent. For cubic crystals like silicon, the semi-empirical sp3d5s* tight-binding (TB) model is preferred in device simulations, over the density functional theory, to obtain the full band structure because of being computationally less intensive and equally accurate. However, the computational time of the TB model scales non-linearly with the channel thickness and becomes cumbersome for silicon, beyond 5 nm, primarily because of the increasing size of the TB hamiltonian that needs to be solved over the entire k-space, in the irreducible Brillouin zone. In this work, we precisely identify those k-points corresponding to the energies close to the band minima, where the Fermi-Dirac probability significantly affects electrostatics parameters. This enables us to demonstrate a computationally efficient approach based on solving the hamiltonian only on those reduced number of k-points. The rigorous benchmarking of the channel electrostatics parameters obtained from this approach is performed with results from accurate full band structure simulations showing excellent agreement over a wide range of channel thicknesses, oxide thicknesses, device temperatures and different channel orientations. By showing that the approach presented in this work is computationally efficient, besides being accurate, regardless of the number of atomic layers, we demonstrate its applicability for simulating UTB devices.

scholarly journals Tight–Binding Analysis of Electronic Structure of Germanene Sheet and Nanoribbons Including Stone-Wales Defect

2021 ◽  
Author(s):  
Komeil Rahmani ◽  
Saeed Mohammadi
Keyword(s):  
Band Structure ◽  
Band Gap ◽  
Energy Band ◽  
Dirac Point ◽  
Tight Binding ◽  
Topological Defects ◽  
Energy Band Structure ◽  
Fermi Velocity ◽  
Tight Binding Approximation ◽  
Wales Defect

Abstract In this paper, we investigate the electronic characteristics of germanene using the tight binding approximation. Germanene as the germanium-based analogue of graphene has attracted much research interest in recent years. Our analysis is focused on the pristine sheet of germanene as well as defective monolayer. The Stone-Wales defect, which is one of the most common topological defects in such structures, is considered in this work. Not only the infinite sheet of germanene but also the germanene nanoribbons in different orientations are analyzed. The obtained results show that applying the Stone–Wales defect into the germanene monolayer changes the energy band structure; the E-k curves around the Dirac point are no longer linear, a band gap is opened, and the Fermi velocity is reduced to half of that of defect-free germanene. In the case of nanoribbon structures, the armchair germanene nanoribbons with nanoribbon widths of 3p and 3p+1 reveal the semiconductor behaviour. However, armchair germanene nanoribbon with width of 3p+2 is semi-metal. After applying the Stone–Wales defect, the band gap of armchair germanene nanoribbons with widths of 3p and 3p+1 is reduced and it is increased for the width of 3p+2. Furthermore, there is no band gap in the energy band structure of zigzag germanene nanoribbon and the metallic behaviour is obvious.

CLASSICAL BAND STRUCTURE OF PERIODIC ELASTIC COMPOSITES

1996 ◽  
Vol 10 (09) ◽  
pp. 977-1094 ◽  
Author(s):  
MANVIR S. KUSHWAHA
Keyword(s):  
Band Structure ◽  
Band Gap ◽  
Binary Systems ◽  
Spectral Gaps ◽  
Wave Localization ◽  
Band Theory ◽  
Phononic Band Gap ◽  
Rich Diversity ◽  
Wide Range ◽  
The Rich

The rich diversity and the fundamental character of the essential theoretical problems associated with it have given band theory a width of interest which contrasts strongly with the apparent narrowness of its subject matter. This review, dealing mainly with the classical band structures of periodic elastic and acoustic binary systems, offers briefly a systematic survey of the historical development of the principles, tools, and applications of band theory for electrons, phonons, photons, and vibrations giving what may be called the "background" to the more recent developments in the fields of photonic and phononic band-gap crystals. Attention is given to survey the physical conditions required to achieve the complete spectral gaps within which the respective propagating modes are utterly forbidden irrespective of the direction of propagation. The existence of complete spectral gaps for cleverly synthesized photonic crystals guarantees the observability of classical Anderson localization of photons and the influence on the spontaneous emission which was, until the 1980's, often regarded as a natural and uncontrollable phenomenon. The phononic band-gap crystals, on the other hand, offer the feasibility of constructing the ultrasound filters, polarization filters, and improvements in designing the transducers, as well as the observability of classical elastic or acoustic wave localization. Abiding by the central theme of the review, numerous theoretical results on the band structure related problems for periodic elastic and acoustic binary sytems have been gathered and reviewed. This survey is preceded by a detailed mathematical machinery that provides the reader with numerous useful analytical results applicable to a wide range of systems of varying interest. Finally, the report concludes with a summary of anticipated implications of photonic and phononic band-gap crystals and proposes some interesting relevant problems concerned with the spectral gaps and the classical wave localization. Our satisfaction in writing this review, like any other review which covers a considerably longer period, was to reach a reasonably self-contained unity by wanting to "leave nothing unexplained". The background provided is believed to make less formidable the task of future writers of reviews in this rather general field and hence enable them to deal more readily with particular aspects of the subject, or with recent advances in those directions in which notable progress may have been made.

Simulation of InAsSb/InGaAs Quantum Dots for Optical Device Applications

2004 ◽  
Vol 851 ◽  
Author(s):  
Paul von Allmen ◽  
Seungwon Lee ◽  
Fabiano Oyafuso
Keyword(s):  
Quantum Dots ◽  
Electronic Structure ◽  
Band Gap ◽  
Atmospheric Chemistry ◽  
Energy Gap ◽  
Tight Binding ◽  
Atomic Interaction ◽  
Optical Detectors ◽  
Wide Range ◽  
Device Applications

ABSTRACTSelf-assembled InAsSb/InGaAs quantum dots are candidates for optical detectors and emitters in the 2–5 micron band with a wide range of applications for atmospheric chemistry studies. It is known that while the energy band gap of unstrained bulk InAs1−xSbx is smallest for x=0.62, the biaxial strain for bulk InAs1−xSbx grown on In0.53Ga0.47As shifts the energy gap to higher energies and the smallest band gap is reached for x=0.51. The aim of the present study is to examine how the electronic confinement in the quantum dots modifies these simple considerations. We have calculated the electronic structure of lens shaped InAs1−xSbx quantum dots with diameter 37 nm and height 4 nm embedded in a In0.53Ga0.47As matrix of thickness 7 nm and lattice matched to an InP buffer. The relaxed atomic positions were determined by minimizing the elastic energy obtained from a valence force field description of the inter-atomic interaction. The electronic structure was calculated with an empirical tight binding approach. For Sb concentrations larger than x=0.5, it is found that the InSb/ In0.53Ga0.47As heterostructure becomes type II leading to no electron confined in the dot. It is also found that the energy gap decreases with increasing Sb content in contradiction with previous experimental results. A possible explanation is a significant variation is quantum dot size with Sb content.

Effects of Structural Disorder on the Electronic Properties of Silicon: Tight-Binding Calculations of Grain Boundaries

1993 ◽  
Vol 297 ◽  
Author(s):  
M. Kohyama ◽  
R. Yamamoto
Keyword(s):  
Band Gap ◽  
Electronic Properties ◽  
Local Density ◽  
Tight Binding ◽  
Structural Disorder ◽  
Local Density Of States ◽  
Deep State ◽  
Amorphous Si ◽  
Semi Empirical ◽  
Twist Boundaries

The atomic and electronic structures of tilt and twist boundaries in Si have been calculated by using the transferable semi-empirical tight-binding (SETB) method, and the relations between the local structural disorder and the electronic properties of Si have been obtained clearly. The odd-membered rings and the four-membered rings induce the changes of the shape of the local density of states (LDOS). The bond distortions generate the peaks at the band edges in the LDOS, and greatly distorted bonds induce the weak-bond states inside the band gap. The three-coordinated defect generates a deep state in the band gap, which is much localized at the three-coordinated atom. The five-coordinated defect generates both deep and shallow states. The deep state is localized in the neighboring atoms except the five-coordinated atom, although the shallow states exist among the five-coordinated atom and the neighboring atoms. Configurations of boundaries are very effective in order to clarify the effects of the local structural disorder in amorphous SI.

Optical band gap of SrTcO3 from first-principles calculations

2014 ◽  
Vol 28 (06) ◽  
pp. 1450049 ◽  
Author(s):  
Cheng-Min Dai ◽  
Chun-Lan Ma
Keyword(s):  
Band Structure ◽  
Band Gap ◽  
Magnetic Moment ◽  
Optical Band Gap ◽  
Tight Binding ◽  
Local Magnetic Moment ◽  
Exchange Constant ◽  
Generalized Gradient ◽  
Direct Band ◽  
State Band

Although there are intensive studies on technetium oxide SrTcO 3 recently, its ground-state band structure has never been given and no consensus on its band gap is obtained. We use the generalized gradient approximation (GGA) with on-site Coulomb corrections (GGA + U) method to study its band structure and the optical band gap. A series of on-site interaction U and J values are employed in the calculations and the concomitant evolutions of the electronic structure, local magnetic moment of technetium ( Tc ), the exchange constant and the Néel temperature are investigated. The inter-site exchange constant between antiferromagnetic Tc atoms through medium oxygen is found to increase firstly and then decrease with an increasing U, in agreement with the trend obtained by tight-binding method. The appropriate on-site U and J values are calibrated by comparing the calculated local magnetic moment of Tc with the experimental value. It is found that when U = 2.3 eV, J = 0.3 eV are included for Tc 4d in GGA + U calculations, the local magnetic moment of Tc in orthorhombic SrTcO 3 is 2.01 μB, the same as the experimental value obtained at 4 K. The calculated band structure shows that the band gap is a direct band gap with a magnitude of 1.61 eV.

Sign in / Sign up

Export Citation Format

Share Document