Researches
Achievement of high efficiency in the thermoelectric characteristics by Si nanostructures
【Researches Goal】Enhancement in Si thermoelectirc characteristics by the electron confinement effect and the phonon transport control
Size effects in Si Seebeck coefficient
We have investigated the Seebeck coefficient of Si nanostructures, especially, ultrathin P-doped SOI (silicon-on-insulator) layers. The dependence of the Seebeck coefficient on the carrier concentration was shown to be in good agreement with that of bulk Si for SOI thicknesses above 6 nm [FIG.1].
FIG.1: Absolute Seebeck coefficient of SOI wafers as a function of impurity concentration. The Seebeck coefficients of Si wafers obtained from our measurements and reported in the literatures are also shown.
The Seebeck coefficient decreased with increasing P concentration, and with a peak of the Seebeck coefficient around 5×10^19 cm^-3. This result indicates that the Seebeck coefficient of the heavily-doped Si is strongly influenced by the impurity band.
We tried to control the Fermi energy of an SOI layer by an external bias. The SOI Seebeck coefficient was found to be modulated by the external bias through the band bending at the SOI/BOX interface [Fig. 2].
We tried to control the Fermi energy of an SOI layer by an external bias. The SOI Seebeck coefficient was found to be modulated by the external bias through the band bending at the SOI/BOX interface [Fig. 2].
FIG.2: Seebeck coefficient of an SOI layer as a function of external bias.
We have examined the composition dependence of SiGe on the phonon drag component of the Seebeck coefficient near room temperature.
About the effective mass and the mobility of carrier, the speed and the mean free path of phonnon, Si has agreed well with the theoretical calculated values interpolated the physical property values of Si Ge and the experimental results. (FIG. 3).
This result shows that the phonon transport contributing to the phonon drug effect has almost no effect of alloy scattering.
About the effective mass and the mobility of carrier, the speed and the mean free path of phonnon, Si has agreed well with the theoretical calculated values interpolated the physical property values of Si Ge and the experimental results. (FIG. 3).
This result shows that the phonon transport contributing to the phonon drug effect has almost no effect of alloy scattering.
FIG.3:
FIG.1: Absolute Seebeck coefficient of SOI wafers as a function of impurity concentration. The Seebeck coefficients of Si wafers obtained from our measurements and reported in the literatures are also shown.
FIG.2: Seebeck coefficient of an SOI layer as a function of external bias.
FIG.3：
【Related Papers】
IEICE Trans. Electron., E-100-C (2017) 486.
IEICE Trans. Electron., E-100-C (2017) 482.
Semicond. Sci. Tech., 32 (2017) 035021.
J. Adv. Phys., 11 (2016) 4088.
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Appl. Phys. Lett., 105 (2014) 102104.
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J. Adv. Res. Phys., 3 (2012) 021207.
Adv. Mater. Res., 222 (2011) 197.
J. Electron. Mater., 40 (2011) 903.
Appl. Phys. Lett., 96 (2010) 012106.
Appl. Phys. Express, 2 (2009) 071203.
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IEICE Trans. Electron., E-100-C (2017) 482.
Semicond. Sci. Tech., 32 (2017) 035021.
J. Adv. Phys., 11 (2016) 4088.
Makara J. Technol., 19 (2015) 21.
Makara J. Technol., 19 (2015) 1.
Adv. Mater. Res., 1117 (2015) 94.
Adv. Mater. Res., 1117 (2015) 86.
Appl. Phys. Lett., 105 (2014) 102104.
Appl. Phys. Lett., 103 (2013) 062107.
J. Adv. Res. Phys., 3 (2012) 021207.
Adv. Mater. Res., 222 (2011) 197.
J. Electron. Mater., 40 (2011) 903.
Appl. Phys. Lett., 96 (2010) 012106.
Appl. Phys. Express, 2 (2009) 071203.
J. Autom. Mobile Rob. Intell. Syst., 3 (2009) 134.
