Vishaal Varahamurthy

Electrical Engineering

Characterization of Rare Earth Doped III-V Thermoelectric Materials

The thermoelectric effect can play a significant role in the global effort to improve energy efficiency by converting waste heat from automobiles, households, and industrial electronics into usable electricity. Prior research has shown III-V semiconductors be highly effective thermoelectric materials. In this study, we will characterize III-V semiconducting materials grown by chemical beam epitaxy and doped with rare earth elements (e.g. erbium, lanthanum). In small amounts, these rare earth dopants affect thermoelectric efficiency by changing the carrier concentration. In larger quantities, the rare earths may precipitate out of the matrix and form nanoparticles, which in theory can further improve device performance by reducing thermal conductivity. We will vary growth parameters such as dopant concentration, growth temperature, and incident flux ratios. The resulting effects of these changes on electrical properties and thermoelectric performance will be measured using the Hall and Seebeck techniques. We predict that the identity of the rare earth dopant will have a minor effect on the electrical characteristics of the material because the rare earth dopants tend to have low solubility and similar ionization energies in III-V materials. Alternatively, the varied growth conditions should have a more significant impact on thermoelectric performance through their effects on the formation, size, and distribution of the rare earth nanoparticles that may precipitate during growth. By observing how these growth parameters affect the material’s thermoelectric performance, we can expand our knowledge of the thermoelectric effect and facilitate research that will improve energy efficiency.

UC Santa Barbara Center for Science and Engineering Partnerships UCSB California NanoSystems Institute