Thermoelectric materials may be used to provide cooling and/or power generation according to the Peltier effect. Thermoelectric materials are discussed, for example, in the reference by Venkatasubramanian et al. entitled “Phonon-Blocking Electron-Transmitting Structures” (18th International Conference On Thermoelectrics, 1999), the disclosure of which is hereby incorporated herein in its entirety by reference.
Application of solid state thermoelectric cooling may be expected to improve the performance of electronics and sensors such as, for example, RF receiver front-ends, infrared (IR) imagers, ultra-sensitive magnetic signature sensors, and/or superconducting electronics.
The performance of a thermoelectric device may be a function of the figure(s)-of-merit (ZT) of the thermoelectric material(s) used in the device, with the figure-of-merit being given by:ZT=(α2Tσ/KT),  (equation 1)where α, T, σ, KT are the Seebeck coefficient, absolute temperature, electrical conductivity, and total thermal conductivity, respectively. The material-coefficient Z can be expressed in terms of lattice thermal conductivity (KL) electronic thermal conductivity (Kc) and carrier mobility (μ), for a given carrier density (ρ) and the corresponding α, yielding equation (2) below:Z=α2σ/(KL+Kc)=α2/[KL/(μσq)+L0)],  (equation 2)where, L0 is the Lorenz number (approximately 1.5×10−8 V2/K2 in non-degenerate semiconductors). State-of-the-art thermoelectric devices may use alloys, such as p-BixSb2-xTe3-ySey (x·0.5, y·0.12) and n-Bi2(SeyTe1-y)3 (y·0.05) for the 200 degree K to 400 degree K temperature range. For certain alloys, KL may be reduced more strongly than μ leading to enhanced ZT.
In addition, thin-film thermoelectric materials have been developed, For example, bismuth telluride (Bi2Te3) and/or antimony telluride (Sb2Te3)-based epitaxial films grown on gallium arsenide (GaAs) substrates may be used in the fabrication of thin-film thermoelectrics. However, the growth morphology of these films may be plagued by cracks and surface defects in the film. For example, a thermoelectric film grown on a 2° offcut GaAs substrate may have a crack density of about 5-20 cracks per millimeter (mm), and in some instances, greater than 10 cracks/mm. These cracks and defects may lead to reliability problems and/or complications in subsequent film processing, which may compromise one or more benefits that may be derived from the films.
Accordingly, there continues to exist a need in the art for improved thermoelectric device fabrication methods and strictures.