Electronic and thermoelectric transport in semiconductor and metallic superlattices

Vashaee, Daryoosh; Shakouri, Ali

doi:10.1063/1.1635992

Cited by 142 publications

(127 citation statements)

References 38 publications

(50 reference statements)

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“…Our approach in this paper is based on the latter assumption and thus can explain the experimental results. 2 Although there is still thermopower anomaly seen in the left-hand side of Fig. 3, the sign of the Seebeck coefficient does not change.…”

Section: Thermoelectric Transport In Minibandmentioning

confidence: 99%

“…We have recently shown that thick and tall barrier superlattices can improve ZT substantially if the lateral momentum of electrons is not conserved in thermionic emission process. 1,2 In this paper, we study thermoelectric transport in short period superlattice structures. Strong coupling between neighboring wells produces minibands.…”

Section: ͑3͒mentioning

confidence: 99%

“…2. The conductivity and Seebeck coefficient can be calculated from the number of electrons participating in transport ͑n e ͒ and the energy transported by these electrons ͑n Q ͒ respectively,…”

Section: Thermoelectric Transport In Minibandmentioning

confidence: 99%

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Cross-plane Seebeck coefficient in superlattice structures in the miniband conduction regime

et al. 2006

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We have studied experimentally and theoretically the cross-plane Seebeck coefficient of short period InGaAs/ InAlAs superlattices with doping concentrations ranging from 2 ϫ 10 18 up to 3 ϫ 10 19 cm −3 . Measurements are performed with integrated thin film heaters in a wide temperature range of 10-300 K. It was interesting to find out that contrary to the behavior in bulk material the Seebeck coefficient did not decrease monotonically with the doping concentration. We did not observe a sign change in the Seebeck coefficient at dopings where the Fermi energy is just above a miniband. This is a sign that electrons' lateral momentum is conserved in the transport perpendicular to superlattice layers. A preliminary theory of thermoelectric transport in superlattices in the regime of miniband formation has been developed to fit the experimental results.

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Section: Thermoelectric Transport In Minibandmentioning

confidence: 99%

Section: ͑3͒mentioning

confidence: 99%

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Cross-plane Seebeck coefficient in superlattice structures in the miniband conduction regime

et al. 2006

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“…18 Venkatasubramanian et al have reported the highest ZT to date, ZT ϳ 2.4, using a p-type Bi 2 Te 3 /Sb 2 Te 3 superlattice. 19 Other methods used and suggested for the enhancement of the figure of merit include the use of quantum-dot superlattices, 20,21 superlatices with a nonconservation of lateral momentum, 22,23 inhomogeneous doping, 24,25 and nanotubes. 26 Many of these approaches offer the possibility of engineering the electron energy spectrum ͑the number of electrons transmitted through the device as a function of energy͒ in a way that was not possible in traditional vacuum thermionics or bulk thermoelectrics.…”

Section: Introductionmentioning

confidence: 99%

“…This model is applicable to vacuum emission from nanostructures such as carbon nanotubes and solid-state devices in which there is periodic modulation of the potential in all three dimensions ͑such as quantum dot superlattices͒, or superlattices in which there is nonconservation of electron momentum in directions perpendicular to transport. 22,23 There are many other physical systems in which the electron emission process is dependent on the total energy of electrons and therefore might be mathematically characterized as a k r system, such as electron emission from electrons. Figure 1 shows geometrically the range of electrons transmitted in idealized k x and k r type devices in momentum space.…”

Section: Introductionmentioning

confidence: 99%

Electronic efficiency in nanostructured thermionic and thermoelectric devices

et al. 2005

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Advances in solid-state device design now allow the spectrum of transmitted electrons in thermionic and thermoelectric devices to be engineered in ways that were not previously possible. Here we show that the shape of the electron energy spectrum in these devices has a significant impact on their performance. We distinguish between traditional thermionic devices where electron momentum is filtered in the direction of transport only and a second type, in which the electron filtering occurs according to total electron momentum. Such "total momentum filtered" thermionic devices could potentially be implemented in, for example, quantum dot superlattices. It is shown that whilst total momentum filtered thermionic devices may achieve an efficiency equal to the Carnot value, traditional thermionic devices are limited to an efficiency below this. Our second main result is that the electronic efficiency of a device is not only improved by reducing the width of the transmission filter as has previously been shown, but also strongly depends on whether the transmission probability rises sharply from zero to full transmission. The benefit of increasing efficiency through a sharply rising transmission probability is that it can be achieved without sacrificing device power, in contrast to the use of a narrow transmission filter which can greatly reduce power. We show that devices that have a sharply rising transmission probability significantly outperform those that do not and that such transmission probabilities may be achieved with practical single and multibarrier devices. We discuss how the shape of the electron energy spectrum will also have an effect on the electronic efficiency of thermoelectric devices due to mathematical equivalences in the ballistic and diffusive formalisms. Finally, we present an experimental measure that might be used to provide an indication of the nature of the electron energy spectrum and the electronic efficiency of a ballistic device.

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Nanostructured Thermoelectrics: Big Efficiency Gains from Small Features

et al. 2010

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The field of thermoelectrics has progressed enormously and is now growing steadily because of recently demonstrated advances and strong global demand for cost-effective, pollution-free forms of energy conversion. Rapid growth and exciting innovative breakthroughs in the field over the last 10-15 years have occurred in large part due to a new fundamental focus on nanostructured materials. As a result of the greatly increased research activity in this field, a substantial amount of new data--especially related to materials--have been generated. Although this has led to stronger insight and understanding of thermoelectric principles, it has also resulted in misconceptions and misunderstanding about some fundamental issues. This article sets out to summarize and clarify the current understanding in this field; explain the underpinnings of breakthroughs reported in the past decade; and provide a critical review of various concepts and experimental results related to nanostructured thermoelectrics. We believe recent achievements in the field augur great possibilities for thermoelectric power generation and cooling, and discuss future paths forward that build on these exciting nanostructuring concepts.

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Electronic and thermoelectric transport in semiconductor and metallic superlattices

Cited by 142 publications

References 38 publications

Cross-plane Seebeck coefficient in superlattice structures in the miniband conduction regime

Cross-plane Seebeck coefficient in superlattice structures in the miniband conduction regime

Electronic efficiency in nanostructured thermionic and thermoelectric devices

Nanostructured Thermoelectrics: Big Efficiency Gains from Small Features

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