InGaAs lattice-matched to InP was grown by molecular beam epitaxy with randomly distributed TbAs nanoparticles for thermoelectric power generation applications. TbAs:InGaAs is expected to have a large thermoelectric figure of merit, ZT, particularly at high temperatures, owing to energy band alignment between the nanoparticles and their surrounding matrix. Here, the room temperature thermoelectricproperties were measured as a function of TbAs concentration, revealing a maximum thermoelectric power factor of 2.38 W/mK2 and ZT of 0.19 with 0.2% TbAs. Trends in the thermoelectricproperties closely resemble those found in comparable ErAs:InGaAs nanocompositematerials. However, nanoparticles were not observed by scanning transmission electron microscopy in the highest ZT TbAs:InGaAs sample, unlike the highest ZT ErAs:InGaAs sample (0.2% ErAs) and two higher concentration TbAs:InGaAs samples examined. Consistent with expectations concerning the positioning of the Fermi level in these materials, ZT was enhanced by TbAs incorporation largely due to a high Seebeck coefficient, whereas ErAs provided InGaAs with higher conductivity but a lower Seebeck coefficient than that of TbAs:InGaAs. Thermal conductivity was reduced significantly from that of intrinsic thin-film InGaAs only with TbAs concentrations greater than ∼1.7%.
This project was funded at UD and UCSC by the Nanostructured Materials for Power program (DARPA-DSO, Army Research Office (Award No. W911NF0810347)) with support from the National Science Foundation IGERT at UD and at UCSB by the National Science Foundation through the UCSB MRL (Award No. DMR 05-20415) and the Army Research Office (Award No. W911NF-0701-0547). We thank Dr. Leszek Wielunski of the Rutgers University Tandem Accelerator Lab for collecting RBS data for these materials and Pernell Dongmo at the University of Delaware for assistance with measurement equipment and error estimation.
II. MATERIAL GROWTH AND PROPERTIES
III. THERMOELECTRIC MEASUREMENTS AND DISCUSSION
IV. SUMMARY AND CONCLUSIONS
- III-V semiconductors
- Thermal conductivity
- Fermi levels
- Thermoelectric effects
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