An innovating technological approach for Si–SiGe superlattice integration into thermoelectric modules

Abstract

This paper presents the development of doped polycrystalline Si-SiGe superlattices as thermoelectric (TE) elements integrated into generators. The modules dimension is 1 cm 2 , Si and SiGe are in situ doped (n and p types) and realized by CVD (chemical vapor deposition) on a 4 inch (0 0 1) silicon wafer. Si-SiGe superlattice growth will be studied, as well as the integration into thermoelectric modules. Interest in using superlattices as TE materials will be justified by their thermal conductivity measurements. Moreover, process fabrication and different geometry designs will be presented. Finally, the first measurements realized on these modules allowed scavenging 320 mV for a temperature difference of 90 K.

Titanium-based silicide quantum dot superlattices for thermoelectrics applications

“…Moreover, the increase in the power factor is obtained here by an increase in the Seebeck coefficient and a stable electrical resistivity, which is the opposite of how it was obtained in the literature [9]. But as explained previously, our references samples have been voluntarily made with the same monocrystalline Si 0.85 Ge 0.15 thin film and about 8 W m −1 K −1 for a Si 0.5 Ge 0.5 monocrystalline bulk sample are in good agreement with the values reported in the literature [4,7].…”

“…This result shows the effect of nanostructuration by including silicide QDs in the reduction of the material's thermal conductivity. Reference values of 6.1 W m −1 K −1 for a monocrystalline Si 0.85 Ge 0.15 thin film and about 8 W m −1 K −1 for a Si 0.5 Ge 0.5 monocrystalline bulk sample are in good agreement with the values reported in the literature [4,7].…”

“…This technique has already been used to successfully grow nanostructured silicon-based thin films [4,13,14].…”

“…For the polycrystalline samples, the electrical resistivity exhibits tiny changes with the temperature. In that case, the scattering on grain boundaries is the dominant scattering effect [4].…”

“…At the short scale, SiGe-based nanostructured materials have already shown a significant decrease in thermal conductivity compared to similar SiGe thin films, Si/SiGe superlattices, and Si x Ge 1−x /Si y Ge 1−y quantum dot superlattices (QDSLs) [4][5][6]. This is mainly due to a reduction of the crystal's lattice thermal conductivity, which is obtained by adding phonon diffusion mechanisms as layer interfaces and nanodots.…”