Thermal conductivity and thermoelectric power of heavily doped n-type silicon

Brinson, Mike; Dunstant, W

doi:10.1088/0022-3719/3/3/001

Cited by 50 publications

(23 citation statements)

References 6 publications

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“…Early theoretical works (1,5,7,26) attempted to concurrently solve the coupled electron-phonon BTEs mostly using a variational approach (1). Although reasonable agreements with experiments were achieved (27,28), the calculations were limited to the lowest orders of the trial functions for the variational method and assumed simplified scattering models, which lack predictive power due to the large number of adjustable parameters involved and make the interpretation of the calculated results less intuitive. An alternative approach to solving the coupled BTEs seeks to partially decouple the electron and phonon transport (29).…”

Section: Significancementioning

confidence: 99%

Ab initio optimization of phonon drag effect for lower-temperature thermoelectric energy conversion

Zhou

Liao

Qiu

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Although the thermoelectric figure of merit zT above 300 K has seen significant improvement recently, the progress at lower temperatures has been slow, mainly limited by the relatively low Seebeck coefficient and high thermal conductivity. Here we report, for the first time to our knowledge, success in first-principles computation of the phonon drag effect-a coupling phenomenon between electrons and nonequilibrium phonons-in heavily doped region and its optimization to enhance the Seebeck coefficient while reducing the phonon thermal conductivity by nanostructuring. Our simulation quantitatively identifies the major phonons contributing to the phonon drag, which are spectrally distinct from those carrying heat, and further reveals that although the phonon drag is reduced in heavily doped samples, a significant contribution to Seebeck coefficient still exists. An ideal phonon filter is proposed to enhance zT of silicon at room temperature by a factor of 20 to ∼0.25, and the enhancement can reach 70 times at 100 K. This work opens up a new venue toward better thermoelectrics by harnessing nonequilibrium phonons.phonon drag | nonequilibrium phonon | electron phonon interaction | thermoelectrics | nanocluster scattering I n metals and semiconductors, lattice vibration-, or phonon-, induced electron scattering has a major influence on electronic transport properties (1). The strength of the electron-phonon interaction (EPI) depends on the distribution of electron and phonon populations. The EPI problem was first studied by Bloch (2), who assumed the phonons to be in equilibrium (so-called Bloch condition) when calculating the scattering rates of electrons caused by EPI, because of the frequent phonon-phonon Umklapp scattering. This assumption is widely adopted for the determination of electronic transport properties at higher temperatures (1, 3), including the electrical conductivity and the normal ("diffusive") Seebeck coefficient. Below the Debye temperature, however, the nonequilibrium phonons become appreciable because the phonon-phonon Umklapp scatterings are largely suppressed, and this assumption becomes questionable. The significance of nonequilibrium phonons on the Seebeck coefficient was first recognized by Gurevich (4). The experimental evidence given later (5, 6) clearly showed an "anomalous" peak of the Seebeck coefficient at around 40 K in germanium. To address this unusual observation, Herring proposed that the nonequilibrium phonons can deliver excessive momenta to the electrons via the EPI (7). This process generates an extra electrical current in the same direction as the heat flow, as if the electrons were dragged along by phonons. Therefore, this effect has been dubbed "phonon drag" (7), which makes itself distinct from the normal (diffusive) Seebeck effect. Subsequent explorations (8-13) revealed that this effect exists in various material systems. In particular, it has been suggested that phonon drag is responsible for the extremely high Seebeck coefficient S = −4,500 μV/K experimentally found i...

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Section: Significancementioning

confidence: 99%

Ab initio optimization of phonon drag effect for lower-temperature thermoelectric energy conversion

Zhou

Liao

Qiu

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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“…Also based upon early investigations [2,3], it was actually computed for instance that in silicon the optimal carrier density for high thermoelectric figures of merit is around 10 18 -10 19 cm À 3 [4]. This notwithstanding, interesting thermoelectric properties were experimentally anticipated for strongly degenerate silicon [5,6]. More recently, an additional body of results has been put forward reporting a concurrent increase of both the electrical conductivity and the Seebeck coefficient in single-crystal silicon [7,8] and unanticipated high power factors in heavily doped polycrystalline silicon [9][10][11] -a series of facts that clearly demand for a revised evaluation of the factors influencing P in degenerate semiconductors.…”

Section: Introductionmentioning

confidence: 97%

Impact of energy filtering and carrier localization on the thermoelectric properties of granular semiconductors

Narducci

Selezneva

Cerofolini

et al. 2012

Journal of Solid State Chemistry

169

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“…From a thermodynamic point of view, the mobilities and the thermopowers have to be regarded as independent transport coefficients, which must be supplied to the modelist, either from measured data [43], [44] or from transport theory [45]. Neglecting low-temperature phenomena such as the phonondrag and other size effects, and assuming nondegenerate conditions, a practical and well-known expression for the thermoelectric power is [46] 4 where s , (a = n,p) sensitively depends on the kind of underlying electron-lattice scattering mechanism.…”

Section: The Thermodynamic Modelmentioning

confidence: 99%

“…If (YO and a1 are equal, (44) can be solved explicitly. After some algebra it follows (a = a0 = a1) :…”

Section: -F Fmentioning

confidence: 99%

Nonisothermal device simulation using the 2D numerical process/device simulator TRENDY and application to SOI-devices

Wolbert

Wachutka

Krabbenborg

et al. 1994

IEEE Trans. Comput.-Aided Des. Integr. Circuits Syst.

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Abstruct-The electrical characteristics of modern VLSI and ULSI device structures may be significantly altered by self-heating effects. The device modeling of such structures demands the simultaneous simulation of both the electrical and the thermal device behavior and their mutual interaction. Although, at present, a large number of multi-dimensional device simulators are available, most of them are based on physical models which do not properly allow for heat transport and other nonisothermal effects.In this paper, we demonstrate that the numerical process/device simulator TRENDY provides a solid base for nonisothermal device simulation, as a physically rigorous device model of carrier and heat transport has been incorporated in the TRENDY program. With respect to the boundary conditions, it is shown that inclusion of an artificial boundary material relaxes some fundamental physical inconsistencies resulting from the assumption of ideal ohmic contact boundaries.The program TRENDY has been used for studying several nonisothermal problems in microelectronics. As an example, we consider an ultra-thin SO1 MOSFET showing that the negative slopes in the V d s -l d s characteristics are caused by the temperature-dependence of the electron saturation velocity.

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Thermal conductivity and thermoelectric power of heavily doped n-type silicon

Cited by 50 publications

References 6 publications

Ab initio optimization of phonon drag effect for lower-temperature thermoelectric energy conversion

Ab initio optimization of phonon drag effect for lower-temperature thermoelectric energy conversion

Impact of energy filtering and carrier localization on the thermoelectric properties of granular semiconductors

Nonisothermal device simulation using the 2D numerical process/device simulator TRENDY and application to SOI-devices

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