TEMPERATURE-DEPENDENT THERMAL-CONDUCTIVITY OF POROUS SILICON

The thermal conductivity lambda(PS) of electrochemically etched porous silicon (PS) layers was determined over a wide temperature range (T = 35-320 K) using the dynamic 3 omega technique. Both the doping level of the silicon wafers (p and p(+)) and the porosity P of the porous la yers (P = 64-89%) were varied. The measured thermal conductivities wer e three to five orders of magnitude smaller than the values for bulk s ilicon. Furthermore, they increase with increasing the wafer doping le vel and with decreasing the porosity P of the layers. For all investig ated PS layers the thermal conductivity increases with temperature. Th e results are discussed in terms of a simple model for heat conduction in PS based on the phonon diffusion model.