An innovative technique for electronic transport model of group-III nitrides

Abstract An optimized empirical pseudopotential method (EPM) in conjunction with virtual crystal approximation (VCA) and the compositional disorder effect is used for simulation to extract the electronic material parameters of wurtzite nitride alloys to ensure excellent agreement with the experiments. The proposed direct bandgap results of group-III nitride alloys are also compared with the different density functional theories (DFT) based theoretical results. The model developed in current work, significantly improves the accuracy of calculated band gaps as compared to the ab-initio method based results. The physics of carrier transport in binary and ternary nitride materials is investigated with the help of in-house developed Monte Carlo algorithms for solution of Boltzmann transport equation (BTE) including nonlinear scattering mechanisms. Carrier–carrier scattering mechanisms defined through Coulomb-, piezoelectric-, ionized impurity-, surface roughness-scattering with acoustic and intervalley scatterings, all have been given due consideration in present model. The direct and indirect energy bandgap results have been calibrated with the experimental data and use of symmetric and asymmetric form factors associated with respective materials. The electron mobility results of each binary nitride material have been compared and contrasted with experimental results under appropriate conditions and good agreement has been found between simulated and experimental results.

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Incomplete Solubility in Nitride Alloys

MRS Proceedings ◽

10.1557/proc-449-871 ◽

1996 ◽

Vol 449 ◽

Cited By ~ 34

Author(s):

I. H. Ho ◽

G.B. Stringfellow

Keyword(s):

Experimental Data ◽

Nearest Neighbor ◽

Solubility Limit ◽

Lattice Parameter ◽

Miscibility Gap ◽

Recent Experimental Data ◽

Virtual Crystal Approximation ◽

Group V ◽

Group Iii ◽

Nitride Alloys

ABSTRACTA model based on the valence-force-field (VFF) model has been developed specifically for the calculation of the irascibility gaps in III-V nitride alloys. In the dilute limit, this model allows the relaxation of the atoms on both sublattices. It was found that the energy due to bond stretching and bond bending was lowered and the solubility limit was increased substantially when both sublattices were allowed to relax to distances as large as the sixth nearest neighbor positions. Using this model, the equilibrium mole fraction of N in GaP was calculated to be 6×l0−7 at 700°C. This is slightly higher than the calculated results from the semi-empirical delta lattice parameter (DLP) model. Both the temperature dependence and the absolute values of the calculated solubility agree closely with the experimental data. The solubility is more than three orders of magnitude larger than the result obtained using the VFF model with the group V atom positions given by the virtual crystal approximation, i.e., with relaxation of only the first neighbor bonds. Other nitride systems, such as GaAsN, AlPN, AlAsN, InPN, and InAsN were investigated as well. The equilibrium mole fractions of nitrogen in InP and InAs are the highest, which agrees well with recent experimental data where high N concentrations have been produced in InAsN alloys. Calculations were also performed for the alloy systems with mixing on the group III sublattice that are so important for device applications. Allowing relaxation to the 3rd nearest neighbor gives an In solubility in GaN at 800°C of less than 6%. Again, this is in agreement with the results of the DLP model calculation. This result may partially explain the difficulties experienced with the growth of these alloys. Indeed, evidence of solid immiscibility has recently been reported. A significant miscibility gap was also calculated for the AlInN system, but the AlGaN system is completely miscible.

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Electronic, optical and thermoelectric properties of new metal-rich homological selenides with palladium–indium: Density functional theory and Boltzmann transport model

Journal of Physics and Chemistry of Solids ◽

10.1016/j.jpcs.2019.109229 ◽

2020 ◽

Vol 138 ◽

pp. 109229 ◽

Cited By ~ 2

Author(s):

Sikander Azam ◽

Souraya Goumri-Said ◽

Saleem Ayaz Khan ◽

Mohammed Benali Kanoun

Keyword(s):

Density Functional Theory ◽

Thermoelectric Properties ◽

Density Functional ◽

Transport Model ◽

Boltzmann Transport ◽

Functional Theory

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Re-examination of the hot-carrier transport model using spherical harmonic expansion of the Boltzmann transport equation

1998 Sixth International Workshop on Computational Electronics. Extended Abstracts (Cat. No.98EX116) ◽

10.1109/iwce.1998.742755 ◽

2002 ◽

Cited By ~ 1

Author(s):

Ting-Wei Tang ◽

Haitao Gan ◽

MeiKei Ieong

Keyword(s):

Transport Equation ◽

Spherical Harmonic ◽

Carrier Transport ◽

Transport Model ◽

Boltzmann Transport Equation ◽

Spherical Harmonic Expansion ◽

Boltzmann Transport ◽

Hot Carrier

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Engineering the Thermal Conductivity of Doped SiGe by Mass Variance: A First-Principles Proof of Concept

Frontiers in Mechanical Engineering ◽

10.3389/fmech.2021.712989 ◽

2021 ◽

Vol 7 ◽

Author(s):

Konstanze R. Hahn ◽

Claudio Melis ◽

Fabio Bernardini ◽

Luciano Colombo

Keyword(s):

Thermal Conductivity ◽

Density Functional ◽

Phonon Scattering ◽

Proof Of Concept ◽

Boltzmann Transport ◽

Third Order ◽

Virtual Crystal Approximation ◽

Density Functional Perturbation Theory ◽

B Doping ◽

Analogous Effect

Thermal conductivity of bulk Si0.5 Ge0.5 at room temperature has been calculated using density functional perturbation theory and the phonon Boltzmann transport equation. Within the virtual crystal approximation, second- and third-order interatomic force constants have been calculated to obtain anharmonic phonon scattering terms. An additional scattering term is introduced to account for mass disorder in the alloy. In the same way, mass disorder resulting from n- and p-type dopants with different concentrations has been included, considering doping with III-group elements (p-type) such as B, Al, and Ga, and with V-group elements (n-type) such as N, P, and As. Little effect on the thermal conductivity is observed for all dopants with a concentration below 1021 cm−3. At higher concentration, reduction by up to 50% is instead observed with B-doping in agreement with the highest mass variance. Interestingly, the thermal conductivity even increases with respect to the pristine value for dopants Ga and As. This results from a decrease in the mass variance in the doped alloy, which can be considered a ternary system. Results are compared to the analogous effect on the thermal conductivity in doped Si.

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Band degeneracy enhanced thermoelectric performance in layered oxyselenides by first-principles calculations

npj Computational Materials ◽

10.1038/s41524-020-00476-3 ◽

2021 ◽

Vol 7 (1) ◽

Author(s):

Ning Wang ◽

Menglu Li ◽

Haiyan Xiao ◽

Zhibin Gao ◽

Zijiang Liu ◽

...

Keyword(s):

Density Functional ◽

Transport Theory ◽

Relaxation Times ◽

Wide Band ◽

Type Systems ◽

Model Systems ◽

Boltzmann Transport ◽

Seebeck Coefficients ◽

Boltzmann Transport Theory ◽

P Type

AbstractBand degeneracy is effective in optimizing the power factors of thermoelectric (TE) materials by enhancing the Seebeck coefficients. In this study, we demonstrate this effect in model systems of layered oxyselenide family by the density functional theory (DFT) combined with semi-classical Boltzmann transport theory. TE transport performance of layered LaCuOSe and BiCuOSe are fully compared. The results show that due to the larger electrical conductivities caused by longer electron relaxation times, the n-type systems show better TE performance than p-type systems for both LaCuOSe and BiCuOSe. Besides, the conduction band degeneracy of LaCuOSe leads to a larger Seebeck coefficient and a higher optimal carrier concentration than n-type BiCuOSe, and thus a higher power factor. The optimal figure of merit (ZT) value of 1.46 for n-type LaCuOSe is 22% larger than that of 1.2 for n-type BiCuOSe. This study highlights the potential of wide band gap material LaCuOSe for highly efficient TE applications, and demonstrates that inducing band degeneracy by cations substitution is an effective way to enhance the TE performance of layered oxyselenides.

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Universal mobility characteristics of graphene originating from charge scattering by ionised impurities

Communications Physics ◽

10.1038/s42005-021-00518-2 ◽

2021 ◽

Vol 4 (1) ◽

Author(s):

Jonathan H. Gosling ◽

Oleg Makarovsky ◽

Feiran Wang ◽

Nathan D. Cottam ◽

Mark T. Greenaway ◽

...

Keyword(s):

Electrical Conductivity ◽

Carrier Density ◽

Carrier Mobility ◽

Carrier Transport ◽

Analytical Models ◽

Pristine Graphene ◽

High Electron ◽

Boltzmann Transport ◽

Transport Parameters ◽

Wide Range

AbstractPristine graphene and graphene-based heterostructures can exhibit exceptionally high electron mobility if their surface contains few electron-scattering impurities. Mobility directly influences electrical conductivity and its dependence on the carrier density. But linking these key transport parameters remains a challenging task for both theorists and experimentalists. Here, we report numerical and analytical models of carrier transport in graphene, which reveal a universal connection between graphene’s carrier mobility and the variation of its electrical conductivity with carrier density. Our model of graphene conductivity is based on a convolution of carrier density and its uncertainty, which is verified by numerical solution of the Boltzmann transport equation including the effects of charged impurity scattering and optical phonons on the carrier mobility. This model reproduces, explains, and unifies experimental mobility and conductivity data from a wide range of samples and provides a way to predict a priori all key transport parameters of graphene devices. Our results open a route for controlling the transport properties of graphene by doping and for engineering the properties of 2D materials and heterostructures.

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Flexoelectricity in atomic monolayers from first principles

Nanoscale ◽

10.1039/d0nr07803d ◽

2020 ◽

Author(s):

Shashikant Kumar ◽

David Codony ◽

Irene Arias ◽

Phanish Suryanarayana

Keyword(s):

Density Functional Theory ◽

Transition Metal ◽

Ab Initio ◽

First Principles ◽

Density Functional ◽

Transition Metal Dichalcogenides ◽

Functional Theory ◽

Group Iii ◽

Flexoelectric Effect ◽

Metal Dichalcogenides

We study the flexoelectric effect in fifty-four select atomic monolayers using ab initio Density Functional Theory (DFT). Specifically, considering representative materials from each of Group III monochalcogenides, transition metal dichalcogenides...

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The influence of the nuclear and atomic form factors on the muon bremsstrahlung cross section

Canadian Journal of Physics ◽

10.1139/p68-251 ◽

1968 ◽

Vol 46 (10) ◽

pp. S377-S380 ◽

Cited By ~ 82

Author(s):

A. A. Petrukhin ◽

V. V. Shestakov

Keyword(s):

Form Factor ◽

Cross Section ◽

Born Approximation ◽

Form Factors ◽

Experimental Results ◽

Simple Analytical Expression ◽

Nuclear Form Factor ◽

The Cross ◽

Atomic Electrons ◽

Bremsstrahlung Process

The cross section for the muon bremsstrahlung process is calculated as a function of the nuclear form factor in the Born approximation following the Bethe and Heitler theory. The influence of the nuclear form factor is greater than that taken by Christy and Kusaka. The simple analytical expression for the effect of the screening of the atomic electrons is found. The influence of a decrease in the cross section upon the interpretation of some experimental results is estimated.

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