Project Details
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Fabrication and characterization of integrated micro-thermoelectric coolers using chemical and physical vapor deposition

Applicants Dr. Heiko Reith, since 12/2020; Professor Dr. Stephan Schulz
Subject Area Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering
Term from 2019 to 2022
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 423406119
 
Final Report Year 2023

Final Report Abstract

Central goal of the current research project was to integrate optimized thermoelectric films obtained from chemical or physical deposition processes in micro thermoelectric coolers (µTECs) to improve their performances. For this purpose, we developed metal organic single source and dual source precursors and investigated their suitability for the deposition of stoichiometric and crystalline thin films of tetradymite-type Sb2Te3, Bi2Te3 and Bi2Se3, respectively, at deposition temperatures below 200 °C. In addition, Physical Vapor Deposition (PVD) experiments were performed at room temperature. The films obtained underwent comprehensive characterization, encompassing their chemical, structural, and thermoelectric properties. To enhance the thermoelectric performance, post-annealing experiments were conducted, which could be carried out after device fabrication. To determine the optimal annealing parameters, the thermoelectric transport properties were studied in-situ during the annealing process. For both the p-type Sb2Te3 and n-type Bi2Te3 materials, the optimal annealing temperature and duration were identified to achieve the best thermoelectric properties. Subsequently, these optimized films were employed in the fabrication of µTECs, utilizing both inplane and out-of-plane device designs. The designs were previously optimized using finite element simulations, considering the thermoelectric properties of the p-type and n-type materials. Initial characterization of the µTECs was performed using thermal reflectance techniques, demonstrating a cooling performance below 2 K. However, this performance was affected by suboptimal contacts, resulting in high contact resistance, as well as surface oxidation of the thermoelectric materials. Nevertheless, the developed cross-plane device design exhibits significant potential for further advancement in micro device development, overcoming the thickness limitations associated with PVD processes. This opens perspectives for high-performance micro modules based on PVD and Chemical Vapor Deposition (CVD) techniques.

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