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 thermoelectric properties 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 thermoelectric properties closely resemble those found in comparable ErAs:InGaAs nanocomposite materials. 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%.

Recently, there has been interest in semimetallic rare earth monopnictide nanoparticles epitaxially embedded in III-V semiconductors due to the drastic changes brought about in these materials' electrical and thermal properties. The properties of terbium codeposited with gallium arsenide by molecular beam epitaxy are discussed here. These new materials were characterized by x-ray diffraction, Rutherford backscattering spectrometry, resistivity measurements, photoluminescence, time-domain thermoreflectance thermal conductivity measurements, optical absorption spectroscopy, and plan-view high-angle annular dark-field scanning transmission electron microscopy. Results revealed successful formation of randomly distributed nanoparticles with an average diameter of ϳ1.5 nm, reduction of thermal conductivity by a factor of about 5, and consistency with theoretical predictions of mid-band-gap Fermi level pinning and behavior of past similar materials. The success of these TbAs:GaAs materials will lead the way for growth of similar materials ͓TbAs:InGa͑Al͒As͔ which are expected to exhibit highly desirable thermoelectric properties.

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The growth and atomic/electronic structure of molecular beam epitaxy (MBE)-grown ErAs nanoparticles and nanorods embedded within a GaAs matrix are examined for the first time via cross-sectional scanning tunneling microscopy (XSTM) and spectroscopy (XSTS). Cross sections enable the interrogation of the internal structure and are well suited for studying embedded nanostructures. The early stages of embedded ErAs nanostructure growth are examined via these techniques and compared with previous 2 cross sectional TEM work. Tunneling spectroscopy I(V) for both ErAs nanoparticles and nanorods was also performed, demonstrating that both nanostructures are semimetallic.