Lishchuk P. Features of thermal transport in porous silicon-based semiconductor structures

The thesis is devoted to the experimental study of thermal properties of porous silicon (PSi) based structures by photoacoustic (PA) gas-microphone technique. A theoretical model describing the formation of PA response in PSi structures with different pore morphology by the PA gas-microphone method in classical configuration is proposed. The model allows to determine thermal conductivity (TC) of porous structures in a wider range of values than by the «critical frequency» model. It was stated that increasing of doping level of the initial Si wafers by 4 orders of magnitude reduces the TC of formed silicon nanowire arrays by 25 times. It was shown that the TC rise of PSi with fractal morphology after the incorporation by liquid is much higher than in systems with well-ordered structure. The TC dependence of amorphous PSi with different porosity on the amorphous fraction was experimentally obtained. It was shown that PA method allows evaluating TC values of PSi with both high porosities and amorphous phase values (> 70%). The dependence of TC of multilayer PSi based systems on the spatial distribution of periodical submicron PSi layers with different porosities was experimentally obtained. The model describing TC of such systems by presence of interfacial thermal resistance between PSi layers is proposed. The dependence of thermal resistance values on differences in porosity values of PSi is obtained.