Fabrication of ultrathin poly-crystalline SiGe-on-insulator layer for thermoelectric applications

Abstract

For realizing high power generator efficiency based on thermoelectricity, Si, Ge and SiGe nanostructures have attracted attention. In this paper, we have investigated a new approach to fabricate an ultrathin polycrystalline SiGe-on-insulator (pc-SGOI) substrate by a simple process based on Si and Ge deposition followed by thermal diffusion suitable for thermoelectric devices. A 45-nmthick SGOI layer with a Ge fraction of nearly 0.45 was fabricated, and the Ge fraction was homogeneous in plane over the layer. Its thermal conductivity was 0.87 W mK −1 , lower than that of a single-crystalline SGOI layer. This is caused by the enhancement of scattering of phonons at grain boundaries in the pc-SGOI layer.

Laser-Driven Phase Segregation and Tailoring of Compositionally Graded Microstructures in Si–Ge Nanoscale Thin Films

“…Such precise spatial control of the material properties opens a route for the fabrication of complex devices based on alloy microstructures such as graded-index optical waveguides and lens, metasurfaces, Bragg gratings, laterally modulated compositional heterostructures, full-spectrum solar cells, multispectral photodetectors, and graded-base transistors, for example. The unexposed material and solute-poor undercladdings surrounding the laser-written regions can be selectively etched to release solute-rich microstripes of nanometer thickness (see Supporting Information, Figure S11), which could be used for the development of microbolometers, thermoelectric generators, and micro-electromechanical systems, where suspended microstructures are required for thermal isolation from the substrate or to allow for movement of parts . Furthermore, this laser-writing procedure could be applied to other multicomponent material systems, including epitaxially-grown crystalline SiGe films, metal alloys (Ni–Cu, Sb–Bi), ternary semiconductors (Al 1– x Ga x As, Hg 1– x Cd x Te, Cd 1– x Zn x Te), ceramics (Al 2 O 3 –Cr 2 O 3 , V 2 O 3 –Cr 2 O 3 ), and organic crystals ( p -chlorobromobenzene– p -dibromobenzene), which behave as pseudobinary systems, having isomorphous phase diagrams similar to that of SiGe alloys …”

Unfolding Band and Absorption Energy Shift of \(\text{Si-Ge}\) Nano Crystals from First-principles Calculations

“…Large thermoelectric figure-of-merits from SiGe nanowires was recently investigated experimentally and computationally [8]. Novel approaches in Si 1−x Ge x nanostructures for high-efficient thermoelectric devices were realized [9,10]. In the fundamental aspects, electrical and optical properties of the alloys are primarily determined by the band structure thereby the crystal structures [11][12][13].…”