Application of the Bridgman Method to Obtain Thermoelectric Silicon Doped with Germanium and Phosphorus

Abstract

Ingots of highly doped silicon Si:P grown by Bridgman directional crystallization with a small (up to 5 at %) fraction of germanium impurity are studied. The main thermoelectric parameters of the material are measured in the temperature range from 50 to 800°C: Seebeck coefficient, electrical conductivity, and thermal conductivity. On the basis of measurement results, the thermoelectric figure of merit determining the efficiency of thermoelectric conversion was calculated. A study of the electrical properties shows that phosphorus from the SiP compound is incorporated into the lattice as a dopant which provides a high concentration of conduction electrons. Chemical analysis of the ingots shows the presence of additional background impurities in them, the concentration and composition of the impurities vary throughout the bulk of the sample. Despite the presence of impurities, the material demonstrates high thermoelectric characteristics, and the efficiency is at the level of the best world results. Further potential for optimization of thermoelectric characteristics owing to the possibility of forming a fine-grained polycrystalline structure is considered.