400 element ErAs:InGaAs/InGaAlAs superlattice power generator
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0886-F12-06.1
400 element ErAs:InGaAs/InGaAlAs superlattice power generator Gehong Zeng, Je-Hyeong Bahk, John E. Bowers Department of Electrical and Computer Engineering, University of California, Santa Barbara, CA 93106 Joshua M. O. Zide, Arthur C. Gossard Materials Department, University of California, Santa Barbara, CA 93106 Yan Zhang, Rajeev Singh, Zhixi Bian and Ali Shakouri Electrical Engineering Department, University of California, Santa Cruz, CA 95064 Woochul Kim, Suzanne Singer, Arun Majumdar Department of Mechanical Engineering, University of California, Berkeley, CA 94720 ABSTRACT We report the fabrication and characterization of thin film power generators composed 400 p- and n-type ErAs:InGaAs/InGaAlAs superlattice thermoelectric elements. The thermoelectric elements incorporate erbium arsenide metallic nanoparticles into the semiconductor superlattice structure to provide charge carriers and create scattering centers for phonons. 10 µm p- and n-type InGaAs/InGaAlAs superlattices with embedded ErAs nano-particles were grown on InP substrates using molecular beam epitaxy. Thermal conductivity values were measured using the 3ω method and cross-plane Seebeck coefficients were determined using Seebeck device test patterns. 400 element ErAs:InGaAs/InGaAlAs thin film power generators were fabricated from superlattice elements 10 µm thick and 200 µm × 200 µm in area. The output power was 4.7 milliwatts for an external electrical load resistor of 150 Ω at about 80 K temperature difference drop across the generator. We discuss the limitations to the generator’s performance and provide suggestions for further improvement. INTRODUCTION The performance of thermoelectric generators is largely dependent on the material 2 figure-of-merit Z = α σ
κ , where α is the material Seebeck coefficient, σ is the electrical
conductivity and κ is the thermal conductivity. A large figure-of-merit ZT is necessary for high power densities and high efficiency. A number of approaches have been pursuing to improve the performance of solid state power generators[1-5]. A lot of research has been done to improve various material thermoelectric properties beyond bulk materials or alloys using superlattice structures[6-12]. Heterostructures can enhance the thermoelectric device performance by the selective emission of hot carriers above the potential barrier through thermionic emission[13]. Low dimensional structures could overcome the efficiency barriers imposed by the physical limit of conventional bulk materials[14-17]. Superlattice interfaces provide phonon scattering centers to reduce the cross-plane thermal conductivity[18]. To achieve high thermoelectric conversion efficiency[19] we suggested using non-planar barriers and embedded quantum dot structures. The incorporation of erbium arsenide metallic nanoparticles into the
0886-F12-06.2
InGaAs/InGaAlAs superlattice can provide both charge carriers and create scattering centers for phonons. In this paper, we report on the fabrication and characterization of 400 element thin film
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