Effect of Quantum-Well Structures on the Thermoelectric Figure of Merit in the Si/Si1-xGex System

1996 ◽  
Vol 452 ◽  
Author(s):  
X. Sun ◽  
M. S. Dresselhaus ◽  
K. L. Wang ◽  
M. O. Tanner
Keyword(s):  
Quantum Well ◽  
Quantum Confinement ◽  
Figure Of Merit ◽  
Molecular Beam ◽  
Theoretical Calculations ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Figure ◽  
Quantum Well Structures ◽  
Quantum Confinement Effects ◽  
Proof Of Principle

AbstractThe Si/Si1-xGex quantum well system is attractive for high temperature thermoelectric applications and for demonstration of proof-of-principle for enhanced thermoelectric figure of merit Z, since the interfaces and carrier densities can be well controlled in this system. We report theoretical calculations for Z in this system, based on which Si/Si1-xGex quantum-well structures were grown by molecular-beam epitaxy. Thermoelectric and other transport measurements were made, indicating that an increase in Z over bulk values is possible through quantum confinement effects in the Si/Si1-xGex quantum-well structures.

Quantum Confinement Effects on the Thermoelectric Figure of Merit in Si/Si1−xGex System

1997 ◽  
Vol 478 ◽  
Author(s):  
X. Sun ◽  
M. S. Dresselhaus ◽  
K. L. Wang ◽  
M. O. Tanner
Keyword(s):  
Quantum Well ◽  
Quantum Confinement ◽  
Figure Of Merit ◽  
Thin Layers ◽  
Thermoelectric Figure Of Merit ◽  
Barrier Width ◽  
Confinement Effects ◽  
Thermoelectric Figure ◽  
Barrier Layers ◽  
Quantum Confinement Effects

AbstractThe Si/Sil−xGex quantum well system is attractive for high temperature thermoelectric applications and for demonstration of proof-of-principle for enhanced thermoelectric figure of merit Z, since the interfaces and carrier densities can be well controlled in this system. We report here theoretical calculations for Z in this system, and results from theoretical modeling of quantum confinement effects in the presence of δ-doping within the barrier layers. The δ-doping layers are introduced by growing very thin layers of wide band gap materials within the barrier layers in order to increase the effective barrier height within the barriers and thereby reduce the barrier width necessary for the quantum confinement of carriers within the quantum well. The overall figure of merit is thereby enhanced due to the reduced barrier width and hence reduced thermal conductivity, K. The δ-doping should further reduce K in the barriers by introducing phonon scattering centers within the barrier region. The temperature dependence of Z for Si quantum wells is also discussed.

Experimental Study of the Effect of the Quantum Well Structures on the Thermoelectric Figure of Merit in Si/Si1-xGex System

1998 ◽  
Vol 545 ◽  
Author(s):  
X. Sun ◽  
J. Liu ◽  
S. B. Cronin ◽  
K. L. Wang ◽  
G. Chen ◽  
...  
Keyword(s):  
Experimental Study ◽  
Quantum Well ◽  
Figure Of Merit ◽  
Quantum Confinement Effect ◽  
Multiple Quantum Well ◽  
Silicon On Insulator ◽  
Multiple Quantum ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Figure ◽  
Quantum Well Structures

AbstractIn bulk form, Si1-xGex is a promising thermoelectric material for high temperature applications. In this paper, we report results from an experimental study as well as theoretical modeling of the quantum confinement effect on the enhancement of the thermoelectric figure of merit. Si/Si1-xGex, multiple quantum well structures are fabricated using molecular beam epitaxy (MBE) on SOI (Silicon-on-Insulator) substrates in order to eliminate substrate effects, especially on the Seebeck coefficient. A method to eliminate the influence of the buffer layer on the thermoelectric characterization is presented. An enhancement of the thermoelectric figure of merit within the quantum well over the bulk value is observed.

New Directions for Nanoscale Thermoelectric Materials Research

2005 ◽  
Vol 886 ◽  
Author(s):  
M. S. Dresselhaus ◽  
Gang Chen ◽  
M. Y. Tang ◽  
R. G. Yang ◽  
H. Lee ◽  
...  
Keyword(s):  
Quantum Well ◽  
Thermoelectric Materials ◽  
Quantum Wire ◽  
Figure Of Merit ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Figure ◽  
Experimental Proof ◽  
New Directions ◽  
Materials Research ◽  
Proof Of Principle

ABSTRACTMany of the recent advances in enhancing the thermoelectric figure of merit are linked to nanoscale phenomena with both bulk samples containing nanoscale constituents and nanoscale materials exhibiting enhanced thermoelectric performance in their own right. Prior theoretical and experimental proof of principle studies on isolated quantum well and quantum wire samples have now evolved into studies on bulk samples containing nanostructured constituents. In this review, nanostructural composites are shown to exhibit nanostructures and properties that show promise for thermoelectric applications. A review of some of the results obtained to date are presented.

The Effect of Quantum Well Structures on the Thermoelectric Figure of Merit

1992 ◽  
Vol 281 ◽  
Author(s):  
L. D. Hicks ◽  
M. S. Dresselhaus
Keyword(s):  
Quantum Well ◽  
Figure Of Merit ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Figure ◽  
Thermoelectric Coolers ◽  
Quantum Well Structures ◽  
Thermoelectric Refrigeration ◽  
Superlattice Structures ◽  
Materials Used ◽  
Made In

ABSTRACTCurrently the materials with the highest thermoelectric figure of merit, Z, are Bi2Te3 alloys. Therefore these compounds are the best thermoelectric refrigeration elements. However, since the 1960's only slow progress has been made in enhancing Z, either in Bi2Te3 alloys or in other thermoelectric materials. So far, the materials used in applications have all been in bulk form. In this paper, it is proposed that it may be possible to increase Z of certain materials by preparing them in quantum well superlattice structures. Calculations have been done to investigate the potential for such an approach, and also to evaluate the effect of anisotropy on the figure of merit. The calculations show that layering has the potential to increase significantly the figure of merit of a highly anisotropic material like Bi2Te3, provided that the superlattice multilayers are made in a particular orientation. This result opens the possibility of using quantum well superlattice structures to enhance the performance of thermoelectric coolers.

Theoretical Modeling of Thermoelectricity in Bi Nanowires

1998 ◽  
Vol 545 ◽  
Author(s):  
X. Sun ◽  
Z. Zhang ◽  
G. Dresselhaus ◽  
M. S. Dresselhaus ◽  
J. Y. Ying ◽  
...  
Keyword(s):  
Numerical Modeling ◽  
Theoretical Model ◽  
Quantum Confinement ◽  
Figure Of Merit ◽  
Wire Diameter ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Figure ◽  
Crystalline Orientation ◽  
One Dimensional ◽  
Bismuth Nanowires

AbstractBismuth as a semimetal is not a good thermoelectric material in bulk form because of the approximate cancellation between the electron and hole contributions. However, quantum confinement can be introduced by making Bi nanowires to move the lowest conduction subband edge up and the highest valence subband edge down to get a one-dimensional (1D) semiconductor at some critical wire diameter dc. A theoretical model based on the basic band structure of bulk Bi is developed to predict the dependence of these quantities on wire diameter and on the crystalline orientation of the bismuth nanowires. Numerical modeling is performed for trigonal, binary and bisectrix crystal orientations. By carefully tailoring the Bi wire diameter and carrier concentration, substantial enhancement in the thermoelectric figure of merit is expected for small nanowire diameters.

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