Electron–phonon interaction in P-, As-, and Sb-doped germanium in the intermediate concentration region

1980 ◽  
Vol 58 (9) ◽  
pp. 1268-1274 ◽  
Author(s):  
V. Radhakrishnan ◽  
P. C. Sharma
Keyword(s):  
Thermal Conductivity ◽  
Conduction Band ◽  
Phonon Scattering ◽  
Metallic State ◽  
Deformation Potential ◽  
Concentration Region ◽  
Electron Phonon Interaction ◽  
Impurity Atoms ◽  
Intermediate Concentration ◽  
Electron Phonon Scattering

The electron–phonon scattering, in the analysis of low temperature thermal conductivity of n-type germanium, is studied in the intermediate donor concentration region. At low concentrations, below metal–insulator transition, the donor electrons are bound to the impurity atoms, and at high concentrations they are free in conduction band. The properties in the intermediate concentration are explained by Mikoshiba's "inhomogeneity model". According to this model, the electrons are in a mixed state both in non-metallic and metallic state. The electron concentrations in the non-metallic and metallic regions are calculated for each sample and the theory of both bound electron–phonon scattering and free electron–phonon scattering are applied. This theory of mixed electron–phonon scattering explains the thermal conductivity results of P-, As-, and Sb-doped germanium samples between 1 and 20 K for intermediate donor concentrations from 1.1 × 1017 to 5.6 × 1017 cm−3. The values of density-of-states effective mass are kept constant (= 0.22) without variation with temperature. The values of shear and dilatation-deformation potential constants are obtained from our calculations. The values of shear-deformation potential for the electrons in the bound region are found to be between 14 and 16 eV, while the values of dilatation-deformation potential are between 1 and 3.5 eV for the electrons in the conduction band and these values are in agreement with the experimentally measured values.

scholarly journals When band convergence is not beneficial for thermoelectrics

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Junsoo Park ◽  
Maxwell Dylla ◽  
Yi Xia ◽  
Max Wood ◽  
G. Jeffrey Snyder ◽  
...  
Keyword(s):  
Charge Carrier ◽  
First Principles ◽  
Design Principle ◽  
Phonon Scattering ◽  
Charge Carrier Concentration ◽  
Deformation Potential ◽  
Interband Scattering ◽  
Improved Performance ◽  
Full Heusler ◽  
Electron Phonon Scattering

AbstractBand convergence is considered a clear benefit to thermoelectric performance because it increases the charge carrier concentration for a given Fermi level, which typically enhances charge conductivity while preserving the Seebeck coefficient. However, this advantage hinges on the assumption that interband scattering of carriers is weak or insignificant. With first-principles treatment of electron-phonon scattering in the CaMg2Sb2-CaZn2Sb2 Zintl system and full Heusler Sr2SbAu, we demonstrate that the benefit of band convergence can be intrinsically negated by interband scattering depending on the manner in which bands converge. In the Zintl alloy, band convergence does not improve weighted mobility or the density-of-states effective mass. We trace the underlying reason to the fact that the bands converge at a one k-point, which induces strong interband scattering of both the deformation-potential and the polar-optical kinds. The case contrasts with band convergence at distant k-points (as in the full Heusler), which better preserves the single-band scattering behavior thereby successfully leading to improved performance. Therefore, we suggest that band convergence as thermoelectric design principle is best suited to cases in which it occurs at distant k-points.

scholarly journals Modeling of Thermoelectric Properties of Semi-Conductor Thin Films With Quantum and Scattering Effects

2006 ◽  
Vol 129 (4) ◽  
pp. 492-499 ◽  
Author(s):  
A. Bulusu ◽  
D. G. Walker
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Thermal Conductivity ◽  
Thermoelectric Properties ◽  
Phonon Scattering ◽  
Quantum Effects ◽  
Effect Of Temperature ◽  
Fundamental Parameters ◽  
Scattering Effects ◽  
Electron Phonon Scattering

Several new reduced-scale structures have been proposed to improve thermoelectric properties of materials. In particular, superlattice thin films and wires should decrease the thermal conductivity, due to increased phonon boundary scattering, while increasing the local electron density of states for improved thermopower. The net effect should be increased ZT, the performance metric for thermoelectric structures. Modeling these structures is challenging because quantum effects often have to be combined with noncontinuum effects and because electronic and thermal systems are tightly coupled. The nonequilibrium Green’s function (NEGF) approach, which provides a platform to address both of these difficulties, is used to predict the thermoelectric properties of thin-film structures based on a limited number of fundamental parameters. The model includes quantum effects and electron-phonon scattering. Results indicate a 26–90 % decrease in channel current for the case of near-elastic, phase-breaking, electron-phonon scattering for single phonon energies ranging from 0.2 meV to 60 meV. In addition, the NEGF model is used to assess the effect of temperature on device characteristics of thin-film heterojunctions whose applications include thermoelectric cooling of electronic and optoelectronic systems. Results show the predicted Seebeck coefficient to be similar to measured trends. Although superlattices have been known to show reduced thermal conductivity, results show that the inclusion of scattering effects reduces the electrical conductivity leading to a significant reduction in the power factor (S2σ).

Electron–Phonon Interaction Model and Prediction of Thermal Energy Transport in SOI Transistor

2007 ◽  
Vol 7 (11) ◽  
pp. 4094-4100 ◽  
Author(s):  
Jae Sik Jin ◽  
Joon Sik Lee
Keyword(s):  
Energy Density ◽  
Group Velocity ◽  
Phonon Scattering ◽  
Phonon Dispersion ◽  
Dispersion Model ◽  
Hot Spot ◽  
Interaction Model ◽  
Phonon Interaction ◽  
Electron Phonon Interaction ◽  
Electron Phonon Scattering

An electron–phonon interaction model is proposed and applied to thermal transport in semiconductors at micro/nanoscales. The high electron energy induced by the electric field in a transistor is transferred to the phonon system through electron–phonon interaction in the high field region of the transistor. Due to this fact, a hot spot occurs, which is much smaller than the phonon mean free path in the Si-layer. The full phonon dispersion model based on the Boltzmann transport equation (BTE) with the relaxation time approximation is applied for the interactions among different phonon branches and different phonon frequencies. The Joule heating by the electron–phonon scattering is modeled through the intervalley and intravalley processes for silicon by introducing average electron energy. The simulation results are compared with those obtained by the full phonon dispersion model which treats the electron–phonon scattering as a volumetric heat source. The comparison shows that the peak temperature in the hot spot region is considerably higher and more localized than the previous results. The thermal characteristics of each phonon mode are useful to explain the above phenomena. The optical mode phonons of negligible group velocity obtain the highest energy density from electrons, and resides in the hot spot region without any contribution to heat transport, which results in a higher temperature in that region. Since the acoustic phonons with low group velocity show the higher energy density after electron–phonon scattering, they induce more localized heating near the hot spot region. The ballistic features are strongly observed when phonon–phonon scattering rates are lower than 4 × 1010 s−1.

The lattice thermal conductivity of silver alloys between 0.3 and 4°K

1965 ◽  
Vol 257 (1083) ◽  
pp. 385-407 ◽  
Keyword(s):  
Thermal Conductivity ◽  
Lattice Thermal Conductivity ◽  
Phonon Scattering ◽  
Copper Alloys ◽  
Mean Free Path ◽  
Copper Sample ◽  
Phonon Interaction ◽  
Temperature Range ◽  
Electron Phonon Interaction ◽  
Electrical Resistivities

The thermal and electrical conductivities of silver and copper alloys with high electrical resistivities were studied in the temperature range from 0.3 to 4 °K. The lattice thermal conductivity results were interpreted in terms of Pippard’s semi-classical theory of the electron-phonon interaction and good qualitative agreement between this theory and the measurements was obtained for the temperature range from 1 to 4 °K. Below 1 °K the thermal conductivity of most samples decreased much more rapidly than one would have expected if the phonon mean free path were limited by the electron-phonon interaction only. Other phonon scattering mechanisms were therefore postulated and the effects of phonon scattering from dislocations was studied both theoretically and experimentally. The increase in thermal resistance below 1 °K of most alloys was more rapid than the increase obtained theoretically for phonon-dislocation and phonon-boundary scattering. The thermal conductivity of a copper sample with a resistance ratio of about 85 was found to be anomalous below 1 °K as well, suggesting that both the phonons and the conduction electrons could contribute to the effect in the alloys.

Electron–Phonon Interaction Model and Prediction of Thermal Energy Transport in SOI Transistor

2007 ◽  
Vol 7 (11) ◽  
pp. 4094-4100
Author(s):  
Jae Sik Jin ◽  
Joon Sik Lee
Keyword(s):  
Energy Density ◽  
Group Velocity ◽  
Phonon Scattering ◽  
Phonon Dispersion ◽  
Dispersion Model ◽  
Hot Spot ◽  
Interaction Model ◽  
Phonon Interaction ◽  
Electron Phonon Interaction ◽  
Electron Phonon Scattering

An electron–phonon interaction model is proposed and applied to thermal transport in semiconductors at micro/nanoscales. The high electron energy induced by the electric field in a transistor is transferred to the phonon system through electron–phonon interaction in the high field region of the transistor. Due to this fact, a hot spot occurs, which is much smaller than the phonon mean free path in the Si-layer. The full phonon dispersion model based on the Boltzmann transport equation (BTE) with the relaxation time approximation is applied for the interactions among different phonon branches and different phonon frequencies. The Joule heating by the electron–phonon scattering is modeled through the intervalley and intravalley processes for silicon by introducing average electron energy. The simulation results are compared with those obtained by the full phonon dispersion model which treats the electron–phonon scattering as a volumetric heat source. The comparison shows that the peak temperature in the hot spot region is considerably higher and more localized than the previous results. The thermal characteristics of each phonon mode are useful to explain the above phenomena. The optical mode phonons of negligible group velocity obtain the highest energy density from electrons, and resides in the hot spot region without any contribution to heat transport, which results in a higher temperature in that region. Since the acoustic phonons with low group velocity show the higher energy density after electron–phonon scattering, they induce more localized heating near the hot spot region. The ballistic features are strongly observed when phonon–phonon scattering rates are lower than 4 × 1010 s−1.

Coupled Non-Equilibrium Green’s Function (NEGF) Electron-Phonon Interaction in Thermoelectric Materials

2011 ◽  
Author(s):  
T. D. Musho ◽  
D. G. Walker
Keyword(s):  
Thermoelectric Materials ◽  
Thermal Transport ◽  
Phonon Scattering ◽  
Computational Method ◽  
Direct Result ◽  
Inelastic Electron ◽  
Phonon Interaction ◽  
Electron Phonon Interaction ◽  
Electron Phonon Scattering ◽  
Non Equilibrium

Over the last decade, nano-structured materials have shown a promising avenue for enhancement of the thermoelectric figure of merit. These performance enhancements in most cases have been a direct result of selectively modifying certain geometric attributes that alter the thermal or electrical transport in a desirable fashion. More often, models used to study the electrical and/or thermal transport are calculated independent of each other. However, studies have suggested electrical and thermal transport are intimately linked at the nanoscale. This provides an argument for a more rigorous treatment of the physics in an effort to capture the response of both electrons and phonons simultaneously. A simulation method has been formulated to capture the electron-phonon interaction of nanoscale electronics through a coupled non-equilibrium Greens function (NEGF) method. This approach is unique because the NEGF electron solution and NEGF phonon solution have only been solved independently and have never been coupled to capture a self-consistent inelastic electron-phonon scattering. One key aspect of this formalism is that the electron and phonon description is derived from a quantum point of view and no correction terms are necessary to account for the probabilistic nature of the transport. Additionally, because the complete phonon description is solved, scattering rates of individual phonon frequencies can be investigated to determine how electron-phonon scattering of particular frequencies influences the transport. This computational method is applied to the study of Si/Ge nanostructured superlattice thermoelectric materials.

scholarly journals A COMPARISON OF THE RESISTIVITY BEHAVIOR OF MgB2, AlB2 AND AgB2 SYSTEMS

2006 ◽  
Vol 20 (16) ◽  
pp. 989-994 ◽  
Author(s):  
R. LAL ◽  
V. P. S. AWANA ◽  
K. P. SINGH ◽  
R. B. SAXENA ◽  
H. KISHAN ◽  
...  
Keyword(s):  
Phonon Scattering ◽  
Weak Localization ◽  
Impurity Scattering ◽  
Phonon Interaction ◽  
Electron Phonon Interaction ◽  
Maximum Minimum ◽  
Electron Phonon Scattering

Measurements have been performed on the resistivity of samples MgB 2, AlB 2 and AgB 2. The samples show presence of impurities. By analyzing the data in terms of impurity scattering, electron-phonon scattering, and weak localization, it has been found that the AlB 2 ( AgB 2) sample involves maximum (minimum) effect of the impurity, electron-phonon interaction and weak localization.

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