Thermoelectrical properties of superlattices Si/Ge

The results of investigation of possible figure of merit increase of thermoelectric materials through the use of superlattices are given. It has been established that phonon thermal conductivity has a considerable effect on the figure of merit of such thermoelectric materials. It has been discovered that additional periodicity caused by the superlattice structure results in phonon spectrum transformation which affects κ_ph. By example of Si_n/Ge_m superlattices the vibration spectrum has been calculated for various number of superlattice layers. It has been also established that thermal conductivity of such systems is decreased as compared to bulk thermal conductivity of Si and Ge. At the same time α and σ increase with reduction of the number of superlattice layers m which indicates the possibility of considerable thermoelectric figure of merit growth for short-period superlattices