Evaluation of Laterally Graded Silicon Germanium Wires for Thermoelectric Devices Fabricated by Rapid Melting Growth

Abstract

To achieve high thermoelectric performance, laterally graded silicon germanium (SiGe) wires were fabricated by rapid melting growth (RMG) method. In addition, the structure evaluation of the RMG laterally graded SiGe wire were performed by Raman spectroscopy and electron backscattering pattern (EBSP). Ge fraction x and strain were estimated from one-dimensional distribution of Raman shift for Ge-Ge mode. As a result, an apparent change of Ge fraction x was observed. For, biaxial isotropic strain assumption, good agreement among the obtained Ge fraction x distribution and theoretical values in the RMG laterally graded SiGe wire near Si seed area were shown. Crystal orientation mapping was obtained by EBSP. It was revealed that the crystal orientation in the SiGe wire was changed from [001] to [110] with increasing growth length. These changes may also influence electronic and thermoelectric performance dramatically.

Local thermal conductivity properties of a SiGe nanowire observed by laser power sweep Raman spectroscopy

“…11,12) Indeed, the material was used in components of the Voyager 13) and New Horizons deep-space craft 14) because of its superior nanoscale low heat conductivity. Moreover, a SiGe nanowire (NW) has been proposed as a structure for next-generation thermoelectric devices 15,16) because it has electrical conductivity comparable to the bulk and its thermal conductivity is lower due to the phonon confinement effect, 17,18) surface roughness, [19][20][21] and alloy 22,23) increasing phonon scattering. Using Eq.…”

Determination of Ge-fraction-shift coefficients for Raman spectroscopy in all vibration modes investigated by single-crystalline bulk SiGe and its application to strain evaluation in SiGe film grown on substrate

“…Silicon-germanium (SiGe) alloy is a promising next-generation material for high-performance transistors [1][2][3] and thermoelectric devices. 4,5) It is important to optimize several parameters in the SiGe thin films and fine structures for each device, e.g. crystal quality, strain states, and Ge fraction.…”

Quantification of Ge fraction using local vibrational modes in Raman spectra of silicon germanium by oil-immersion Raman spectroscopy

“…Silicon germanium (SiGe) is a promising candidate for nextgeneration materials for high-performance transistors, 1,2) optoelectronic devices, 3) and thermoelectric devices. [4][5][6] For each device, it is important to optimize several parameters, e.g. crystal quality, strain states and Ge fraction, in the SiGe thin films and fine structures.…”