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.

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.

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.

Use of Quantum-Well Superlattices to Increase the Thermoelectric Figure of Merit: Transport and Optical Studies

1994 ◽  
Vol 358 ◽  
Author(s):  
L. D. Hicks ◽  
X. X. Bi ◽  
M. S. Dresselhaus
Keyword(s):  
Quantum Well ◽  
Figure Of Merit ◽  
Thermoelectric Device ◽  
Thermoelectric Figure Of Merit ◽  
Optical Studies ◽  
Thermoelectric Figure ◽  
Optical Techniques ◽  
Materials Used

ABSTRACTThe thermoelectric figure of merit (ZT) of a material is a measure the usefulness of the material in a thermoelectric device. Presently, the materials with the highest ZT are Bi2Te3 alloys, with ZT ≃ 1. There has been little improvement in ZT for over 30 years. So far, all the materials used in thermoelectric applications have been in bulk form. Recently, however, calculations have shown that it may be possible to increase ZT of some materials through the use of quantum-well superlattices. We have made preliminary measurements on the Bi/PbTe superlattice system using transport and optical techniques to determine whether it is possible to achieve such an increase in ZT.

Thermoelectric Transport in Superlattices

1997 ◽  
Vol 478 ◽  
Author(s):  
T. L. Reinecke ◽  
D. A. Broido
Keyword(s):  
Exact Solution ◽  
Figure Of Merit ◽  
Phonon Scattering ◽  
Thermoelectric Figure Of Merit ◽  
Thermoelectric Figure ◽  
Thermoelectric Transport ◽  
Barrier Layers ◽  
Thermoelectric Transport Properties ◽  
Carrier Tunneling

AbstractThe thermoelectric transport properties of superlattices have been studied using an exact solution of the Boltzmann equation. The role of heat transport along the barrier layers, of carrier tunneling through the barriers, of valley degeneracy and of the well width and energy dependences of the carrier-phonon scattering rates on the thermoelectric figure of merit are given. Calculations are given for Bi2Te3 and for PbTe, and the results of recent experiments are 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.

Sign in / Sign up

Export Citation Format

Share Document