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

Vashaee, Daryoosh; Zhang, Yan; Shakouri, Ali; Zeng, Gehong; Chiu, Yi-Jen

doi:10.1103/physrevb.74.195315

Cited by 46 publications

(29 citation statements)

References 13 publications

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“…In brief, electron transport is modeled by a bulk-type linear Boltzmann equation with a correction due to the quantum mechanical transmission above and below the barrier. Since the optimum Fermi energy is close to barrier height and 3D states contribute significantly to electronic transport, it is also important to consider both 2D states in the wells and 3D states in the barrier.. We further verified the theory by analyzing the cross-plane Seebeck coefficient in short period InGaAs/InAlAs superlattices (lattice matched in InP) [ 11 ]. In these structures, as the doping is increased, the Seebeck coefficient shows a non-monotonic behavior.…”

Section: Solid-state Devices Theoretical Analysismentioning

confidence: 49%

Solid-State and Vacuum Thermionic Energy Conversion

Shakouri¹,

Bian²,

Singh³

et al. 2005

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A brief overview of the research activities at the Thermionic Energy Conversion (TEC) Center is given. The goal is to achieve direct thermal to electric energy conversion with >20% efficiency and >1W/cm 2 power density at a hot side temperature of 300-650C. Thermionic emission in both vacuum and solid-state devices is investigated. In the case of solid-state devices, hot electron filtering using heterostructure barriers is used to increase the thermoelectric power factor. In order to study electron transport above the barriers and lateral momentum conservation in thermionic emission process, the currentvoltage characteristic of ballistic transistor structures is investigated. Embedded ErAs nanoparticles and metal/semiconductor multilayers are used to reduce the lattice thermal conductivity. Cross-plane thermoelectric properties and the effective ZT of the thin film are analyzed using the transient Harman technique. Integrated circuit fabrication techniques are used to transfer the n-and p-type thin films on AlN substrates and make power generation modules with hundreds of thin film elements. For vacuum devices, nitrogen-doped diamond and carbon nanotubes are studied for emitters. Sb-doped highly oriented diamond and low electron affinity AlGaN are investigated for collectors. Work functions below 1.6eV and vacuum thermionic power generation at temperatures below 700C have been demonstrated. Report Documentation Page INTRODUCTIONDirect thermal to electrical energy conversion systems that could operate at lower temperatures (300-650C) with high efficiencies (>15-20%) provide an attractive compact alternative to internal combustion engines for many applications in the W-MW range. They will also expand the possibilities for waste heat recovery applications. The Thermionic Energy Conversion Center's goal is to design, fabricate, and characterize direct energy conversion systems that meet the above requirements. The core of the solution is an integrated approach to engineer electrical and thermal properties of nanostructured materials and devices and fabricate more efficient solid-state and vacuumbased thermionic energy conversion systems. Solid-state material design is focused on increasing the efficiency of heterostructure thermionic power generators using embedded nanoparticles and metal/semiconductor superlattices. Vacuum effort focuses on the development of thermionic energy conversion based on thermionic-field emission from nanostructured carbon surfaces and low work function n-type wide band gap semiconductor collectors. Measurements of electrical, optical and thermal transport at both the device and nanostructure level are used to verify model predictions and thereby lay the foundation for improved device and materials design. Finally, various components will be integrated and packaged for systems demonstration. Fig. 1 displays a chart of the research groups participating in the Thermionic Energy Conversion Center.

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Section: Solid-state Devices Theoretical Analysismentioning

confidence: 49%

Solid-State and Vacuum Thermionic Energy Conversion

Shakouri¹,

Bian²,

Singh³

et al. 2005

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“…Typically, the optimal Fermi level is about similar for bulk and superlattices within $k B T but the Fermi level of superlattices in reference to the conduction-band minimum of barriers. 9,10 When the superlattice transport is optimized, the Seebeck coefficient can be enhanced at the same time that the group velocity is only slightly reduced from the bulk value near the edge of the barrier conductionband minimum. However, the required doping level, higher than in the bulk, makes the impurity scattering stronger and thus the electron mobility smaller.…”

Section: Resultsmentioning

confidence: 99%

“…The performance of the III-V superlattices has been successfully explained by miniband transport calculations previously. 9 In this work, we extend the method proposed in Ref. 9 to theoretically investigate the thermoelectric transport via minibands in InGaAlAs/InGaAs III-V semiconductor superlattices at low temperatures.…”

Section: Introductionmentioning

confidence: 99%

“…9 In this work, we extend the method proposed in Ref. 9 to theoretically investigate the thermoelectric transport via minibands in InGaAlAs/InGaAs III-V semiconductor superlattices at low temperatures. We calculate the thermoelectric power factors in various conditions of the III-V superlattices, and show that the Seebeck coefficient can be significantly enhanced by utilizing the sharp features in the DOS in the miniband transport in particular at low temperatures when the electron distribution that contributes to conduction is sufficiently narrow.…”

Section: Introductionmentioning

confidence: 99%

“…8 Vashaee et al suggested that the thermoelectric power factor can be significantly enhanced through the transport in multiple minibands in particular when the lateral momentum is not conserved. 9 However, the variation of group velocity by the miniband transport was ignored in the work, and thus the power factor enhancement was overestimated. Recently, Bian et al accurately calculated the variation of group velocity and the Lorenz number in miniband transport to estimate the thermoelectric figure of merit of III-V semiconductor superlattices at high temperatures above room temperatures.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Seebeck Enhancement Through Miniband Conduction in III–V Semiconductor Superlattices at Low Temperatures

Bahk

Sadeghian

Bian

et al. 2012

Journal of Elec Materi

Self Cite

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We present theoretically that the cross-plane Seebeck coefficient of InGaAs/ InGaAlAs III-V semiconductor superlattices can be significantly enhanced through miniband transport at low temperatures. The miniband dispersion curves are calculated by self-consistently solving the Schrödinger equation with the periodic potential, and the Poisson equation taking into account the charge transfer between the two layers. Boltzmann transport in the relaxation-time approximation is used to calculate the thermoelectric transport properties in the cross-plane direction based on the modified density of states and group velocity. It is found that the cross-plane Seebeck coefficient can be enhanced more than 60% over the bulk values at an equivalent doping level at 80 K when the Fermi level is aligned at an edge of the minibands. Other thermoelectric transport properties are also calculated and discussed to further enhance the thermoelectric power factor.

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Record High Power Factor and Low Thermal Conductivity in Amorphous/PbTe/Amorphous Multiple Quantum Wells

Ning

Dong

Jian

et al. 2023

Adv Funct Materials

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Quantum well (QW) superlattice is one of the proposals to improve the thermoelectric properties and provide a rich platform for the next generation of thermoelectric device. Previous QW have two main challenges that need to be addressed: i) decrease the electron tunneling across the layers in the semiconductor‐based multiple QWs (MQW), and ii) decrease the thermal conductivity in the oxide‐based MQW. Herein, the study demonstrates amorphous based PbTe/amorphous‐STO MQWs with ultrahigh power factor of 40.9 µW cm−1 K−2 and record low thermal conductivity of ≈0.49 W m−1 K−1 at room temperature. The high performance of PbTe/amorphous‐STO MQWs is attributed to strong quantum confine effect and its intrinsic low thermal conductivity of amorphous superlattice structure. The results open up a new avenue toward modulating thermoelectric properties beyond traditional MQWs of thermoelectric materials.

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

Cited by 46 publications

References 13 publications

Solid-State and Vacuum Thermionic Energy Conversion

Solid-State and Vacuum Thermionic Energy Conversion

Seebeck Enhancement Through Miniband Conduction in III–V Semiconductor Superlattices at Low Temperatures

Record High Power Factor and Low Thermal Conductivity in Amorphous/PbTe/Amorphous Multiple Quantum Wells

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