Thermal conductivity of indium phosphide-based superlattices

Semiconductor superlattice structures have shown promise as thermoelectric materials for their high power factor and low thermal conductivity. While t he power factor of a superlattice can be controlled through band gap engine ering and doping, prediction and control of thermal conductivity has remain ed a challenge. The thermal conductivity of three different InP/InGaAs supe rlattices was measured to be between 4 and 9 W/m-K from 77-320 K using the 3 omega method. Although the thermal conductivity of InP is an order of mag nitude higher than that of InGaAs, we report the intriguing observation tha t as the fraction of InP is increased in InP/InGaAs superlattices, the ther mal conductivity decreases. For one superlattice, the thermal conductivity was even below that of InGaAs. These observations are contrary to predictio ns of effective thermal conductivity by the Fourier law.