Finite Element Analysis of Miniature Thermoelectric Cooler for the Thermal Management of Si-Based Photonic Integrated Circuits

Abstract

Today’s electronic and photonic devices are facing a bottleneck in removing and managing the excess heat flux due to its progressive miniaturization and integration density. Generation of high heat flux during device operation has become a major challenge and makes the Si-based photonic integrated circuits (PIC) less efficient to function at the desired temperature. Hence, it is essential to remove/ manage the heat flux to maintain efficient and reliable operation of the device. The state-of-art solution to control device temperature involves macro thermoelectric coolers (TEC), which are inefficient in meeting the thermal management requirement for photonic integrated circuits (PIC). Thermal management of these optoelectronic chips using a micro-thermoelectric coolers (µTECs) can be a better proposition, as it can be integrated directly on the photonic chip by removing the large macro-TECs, which will allow precise control of the thermal load [1]. µTECs integrated with optoelectronic devices (lasers, modulators, etc.) can handle large heat flux, with fast response time and can provide high device performance with reduced cost [2].In this work, a comprehensive study focusing on the cooling performance of the µTECs for a photonic package is performed by finite element method (FEM) using COMSOL Multiphysics software. All the simulations and design optimizations have been done following the microfabrication constraints along with the realistic heat flux scenarios. In order to enable the full potential of silicon-based photonic devices, we considered Si as the substrate. The effect of parameters such as load current, the thickness and shape of the thermoelectric pillars, thickness of the interconnect material and number of thermoelectric pillars on device cooling performance are optimized. It is known that bismuth-telluride (Bi-Te) based thermoelectric materials currently have the highest cooling performance near room temperature. For design optimization, first, a single uni-pair is considered and thermoelectric properties of electrodeposited CuTe and BiSbTe are selected as the n- and p-type thermoelectric materials [3, 4]. Also, the effect of substrate, which significantly influences the heat flow between the µTEC and atmosphere is studied. The results indicate that with increasing the leg height, first ΔT increases and later decreases due to joule heating while the coefficient of performance (COP) decreases. A range of load current (I) between 5 to 450 mA is applied and a maximum temperature difference of around 35 K is achieved at 250 mA. In summary, µTEC can be better choice as opposed to macro-TEC in terms of energy efficiency with the benefit of using less toxic materials, which may pave the way of future highly integrated optoelectronic circuits. Acknowledgments This work received funding from the European Union’s Horizon 2020 Research and Innovation Programme under Grant Agreement No. 825114 (SmartVista). This publication has emanated from research supported in part by a research grant from Science Foundation Ireland (SFI) and is co-funded under the European Regional Development Fund under Grant Number 15/IA/3160, 12/RC/2276 and 13/RC/2077 References R. Enright, S. Lei, K. Nolan, I. Mathews, A. Shen, G. Levaufre, R. Frizzell, G. H. Duan and D. Hernon, Bell Labs Technical Journal, 19, 31 (2014). S. Corbett, D. Gautam, S. Lal, K. Yu, N. Balla, G. Cunningham, K. M. Razeeb, R. Enright and D. McCloskey, ACS Applied Materials & Interfaces, 13, 1773 (2021). S. Lal, K. M. Razeeb and D. Gautam, ACS Applied Energy Materials, 3, 3262 (2020). S. Lal, D. Gautam and K. M. Razeeb, APL Materials, 7, 031102 (2019). Figure 1