The impact of commonly used approximations on the computation of the Seebeck coefficient and mobility of polar semiconductors

Ramu, Ashok T.; Bowers, John E.

doi:10.1063/1.4764517

Cited by 9 publications

(6 citation statements)

References 27 publications

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“…In order to calculate the mobility and Seebeck coefficient, we solve the Boltzmann transport equation (BTE) using Rode's iterative method 3,8,[11][12][13][14][15][16][17] (Appendix A 2) to obtain the electron distribution in response to a small driving force (e.g. a small electric field or a small temperature gradient).…”

Section: A Solution To the Boltzmann Transport Equationmentioning

confidence: 99%

Ab initioelectronic transport model with explicit solution to the linearized Boltzmann transport equation

Faghaninia

Ager

2015

Phys. Rev. B

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Accurate models of carrier transport are essential for describing the electronic properties of semiconductor materials. To the best of our knowledge, the current models following the framework of the Boltzmann transport equation (BTE) either rely heavily on experimental data (i.e., semi-empirical), or utilize simplifying assumptions, such as the constant relaxation time approximation (BTE-cRTA). While these models offer valuable physical insights and accurate calculations of transport properties in some cases, they often lack sufficient accuracy -particularly in capturing the correct trends with temperature and carrier concentration. We present here a transport model for calculating low-field electrical drift mobility and Seebeck coefficient of n-type semiconductors, by explicitly considering relevant physical phenomena (i.e. elastic and inelastic scattering mechanisms). We first rewrite expressions for the rates of elastic scattering mechanisms, in terms of ab initio properties, such as the band structure, density of states, and polar optical phonon frequency.We then solve the linear BTE to obtain the perturbation to the electron distribution -resulting from the dominant scattering mechanisms -and use this to calculate the overall mobility and Seebeck coefficient. Using our model, we accurately calculate electrical transport properties of the compound n-type semiconductors, GaAs and InN, over various ranges of temperature and carrier concentration. Our fully predictive model provides high accuracy when compared to experimental measurements on both GaAs and InN, and vastly outperforms both semi-empirical models and the BTE-cRTA. Therefore, we assert that this approach represents a first step towards a fully ab initio carrier transport model that is valid in all compound semiconductors. 73.61.Ey, 71.20.Nr

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Section: A Solution To the Boltzmann Transport Equationmentioning

confidence: 99%

Ab initioelectronic transport model with explicit solution to the linearized Boltzmann transport equation

Faghaninia

Ager

2015

Phys. Rev. B

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“…Both the resistivity and absolute value of the thermopower along the [11

\overset{true¯}{2}

] NbO 2 was pretty small as compared with other directions. Experimentally obtained electron carrier effective mass in the [11

\overset{true¯}{2}

] direction was surprisingly small, only 0.051 m e , which is similar to that of high‐mobility GaAs and InSb . Since simple metal oxides have several advantages against complex oxides in view of easy fabrication, the present results would be beneficial for realizing advanced electronic devices using simple metal oxides.…”

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confidence: 54%

Extremely Light Carrier‐Effective Mass in a Distorted Simple Metal Oxide

Kim

Zhang

Tong

et al. 2018

Adv Elect Materials

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conductivity, [1][2][3][4] many researches have been studied thus far. Among these exotic properties, Q1D conductivity of complex metal oxides can be often explained by simple toy model on the structureproperty relation because such complex metal oxides have complicated crystal structures. For example, crystal structure of Q1D conducting SrNbO 3.4+δ[5] and Ba 1.2 Rh 8 O 16[6] is composed of MO 6 octahedra (M is Nb for SrNbO 3.4+δ and Rh for Ba 1.2 Rh 8 O 16 ), and their connectivity through the edge and/or corners plays a critical role to form conducting channels. In these complex metal oxides, the alkaline earth ions play an essential role to determine the crystallographic asymmetry or distortion. Thus, the direction of the conducting channels could be determined by the alkaline earth ions (Figure 1a).For the practical application of Q1D conducting materials, simple metal oxides are more important than complex oxides in view of easy fabrication. Although simple metal oxides with distorted crystal structures could also be expected to show anisotropic electron transport properties, there are a few attempts to find Q1D conductivity in relatively simple structures such as rutile and perovskite structures (Figure 1b), even if those structures can be easily affected by Exotic electron transport properties such as quasi 1D conductivity are useful to realize advanced electronic devices showing unique properties. Anisotropic electron transport properties are often found in complex metal oxides due to their complicated crystal structures. Although simple metal oxides with distorted crystal structures could also be expected to show anisotropic electron transport properties, it is rarely studied most likely due to the lack of their high-quality epitaxial films. Here anisotropic electron transport properties, showing "fast electron transport path," in a simple distorted metal oxide, NbO 2 , is reported. High-quality NbO 2 epitaxial films with different crystallographic orientations on (0001) and (11 102) α-Al 2 O 3 single crystal substrates are fabricated, and the electron transport properties at room temperature are measured. Both the resistivity and absolute value of the thermopower along the [112] NbO 2 is pretty small as compared with other directions. Experimentally obtained electron carrier effective mass in the [112] direction is surprisingly small, only 0.051 m e , which is similar to that of high-mobility GaAs. Since simple metal oxides have several advantages against complex oxides in view of easy fabrication, the present results will be beneficial for realizing advanced electronic devices using simple metal oxides.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/aelm.201800504.Exotic electron transport properties are useful to realize advanced electronic devices showing unique properties. Since complex metal oxides show many exotic electron transport properties such as superconductivity, metal-to-insulator transition (MIT), gigantic thermopower, and qu...

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“…To this end, we derived general expressions for the heat-flux and temperature by means of spherical harmonic expansions (SHEs) of the distribution functions for the HF and LF components. For bulk electron transport, even low-order SHEbased BTE solutions are known to give excellent agreement with experimental results [16][17] [18]. Our procedure results in an analytical model for heat transport that eschews the notion of a local temperature for the LF modes.…”

mentioning

confidence: 68%

A Compact Enhanced Fourier Law for Next-Generation Device Thermal Modelling

Ramu

Bowers

2015

Proceeding of Proceedings of CHT-15. 6th International Symposium on ADVANCES IN COMPUTATIONAL HEAT TRANSFER , May 25-29, 2015,

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In light of the findings of Johnson et al. that ballistic phonons with mean-free paths upto 500 microns carry a significant fraction of the total heat-flux in silicon at room temperature, it has become imperative to include ballistic transport effects in electronic and optoelectronic device thermal simulations even in the microscale. It would be impractical, in the short run at least, to shift to a fully numerical solution of the Boltzmann transport equation (BTE) for phonon transport. Coupling such a numerical solver with electron distributions and optical fields will be very time consuming, over and above the demanding computational requirements of the BTE solution itself. We present here an alternative, the "enhanced Fourier law", which retains the mathematical brevity and simplicity of the Fourier law while including important ballistic transport effects. Rigorous derivation starting from the BTE lends clear physical meanings to various parameters in our equations, as opposed to so-called "phenomenological" models containing large numbers of essentially numerical fitting parameters. Two illustrative applications are considered: (a) deviations from the Fourier law reported by Johnson et al. using the transient gratings experiment, and (b) a serious difficulty in extracting the mean-free path accumulation function from frequency-domain thermoreflectance experiments-a difficulty that has not been pointed out until now. The enhanced Fourier law is expected to be of great promise to industrial device simulation because of the detailed information it yields about the heat-flux resolved according to the mean-free path, or in other words, according to the length scale of scattering. NOMENCLATURE = the net heat-flux.

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The impact of commonly used approximations on the computation of the Seebeck coefficient and mobility of polar semiconductors

Cited by 9 publications

References 27 publications

Ab initioelectronic transport model with explicit solution to the linearized Boltzmann transport equation

Ab initioelectronic transport model with explicit solution to the linearized Boltzmann transport equation

Extremely Light Carrier‐Effective Mass in a Distorted Simple Metal Oxide

A Compact Enhanced Fourier Law for Next-Generation Device Thermal Modelling

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