Free-standing planar thin-film thermoelectric microrefrigerators and the effects of thermal and electrical contact resistances

Thermoelectric microrefrigerators provide an attractive solid-state solution for on-chip thermal management of microelectronics due to their unique advantages. Here we propose a free-standing planar design of thermoelectric microrefrigerator based on thin film technologies to address the high-performance on-chip cooling and compatibility with microelectronics fabrication. By combining theoretical modeling, numerical simulations and experiments, we conducted a comprehensive investigation of the steady-state and transient performances of the proposed microrefrigerators and various factors that might influence their performance, such as contact resistances, element geometries, convection and radiation, have been explored. Both thermal and contact resistances are found to be important for the cooling performance of the proposed microrefrigerators while they play different roles on the cold and hot sides of a refrigerator. The influence of contact resistances on the design strategies of a microrefrigerator is also discussed. It is demonstrated that microrefrigerators based on IC-compatible low-cost SiGe thin films can potentially achieve a cooling temperature more than 20 K with a response time shorter than 40 ms near room temperature, rendering them competitive against the state-of-the-art microrefrigerators based on toxic conventional heavy metal thermoelectrics such as Bi2Te3 and Sb2Te3.