Importance of electron-phonon coupling in thermal transport in metal/semiconductor multilayer films

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Thermal transport across the interface between metals and semiconductors is ubiquitous in micro- and nano-manufacturing devices. The direct simulation of thermal transport in such multilayers is rarely studied due to different main carriers involved, such as electrons in metals and phonons in semiconductors. This study investigates thermal transport in metal/semiconductor multilayer films using the coupled electron and phonon Boltzmann transport equations combined with the phonon diffuse mismatch model. The calculated overall thermal conductivity demonstrates the importance of electron-phonon coupling transport and then the present work gives a critical thickness of the metal layer for considering electron-phonon coupling transport. If only one side of the metal layer is in contact with the semiconductor, the electron-phonon coupling transport in metal layer should be considered when the metal layer thickness is larger than 12.5 nm, 7.5 nm and 2 nm for Au/Si, Cu/Si and Al/Si bilayer films, respectively. This critical thickness will be approximately double if two sides of the metal layer are both in contact with the semiconductor due to the non-equilibrium between electrons and phonons at both sides, such as the super-lattice with infinity periods. Additionally, there exist a minimum thermal conductivity in metal/semiconductor multilayers when changing the thickness of the metal layer. This work will promote a deeper understanding of the thermal transport in metal/semiconductor multilayers at the micro and nanoscale and provide the insightful indication for the manipulation of thermal conductivity in multilayers.