Impact of porous silicon thickness on thermoelectric properties of silicon-germanium alloy films produced by electrochemical deposition of germanium into porous silicon matrices followed by rapid thermal annealing

Silicon-germanium alloy films were formed by electrochemical deposition of germanium into porous silicon matrices with thicknesses varying from 1.5 to 10 μm followed by subsequent rapid thermal processing at 950 °C in an inert atmosphere. Study of the fabricated structures using SEM and Raman spectroscopy, as well as measurements of their electrical conductivity and thermoelectric properties revealed that the highest Seebeck coefficient (−505 μV/K at 450 K) and Power Factor (1950 μW/(m·K2) at 400 K) values were obtained when a 5 μm-thick porous silicon was used as a structural matrix. Under such conditions, an optimal balance between electrical conductivity, structural disorder and electrical insulation from the substrate is achieved due to the presence of a residual porous underlayer, making it possible to maximize the film's thermoelectric performance. The obtained silicon-germanium alloy films are deemed suitable for the fabrication of both discrete and integrated thermoelectric devices based on monocrystalline silicon substrates. •Si1-xGex layers were produced by thermal annealing of Ge-filled porous silicon.•Porous silicon thickness was varied to evaluate its effect on alloy films.•Residual porous layer is present under alloy film when thick porous silicon is used.•Residual porous layer is shown to provide film-substrate electrical insulation.•Improved insulation is shown to lead to improved thermoelectric performance.