Hotspot and nonequilibrium thermal transport in AlGaN/GaN FinFET: A coupled electron-phonon Monte Carlo simulation study

Due to the unavoidable electron-phonon scattering, field effect transistor experiences severe self-heating effect. The nonequilibrium thermal transport process induced by hotspot exhibits greater thermal resistance and more complex transport mechanisms compared to macroscale thermal transport. In this study, a method combining TCAD, first-principle calculation, and coupled electron-phonon Monte Carlo simulation was used to model AlGaN/GaN FinFET. We systematically investigated the mechanisms of hotspot formation and the resulting temporal and spatial nonequilibrium thermal transport processes. For the conditions adopted in this work, the hotspot primarily arises from the emission process of polar optical scattering, with peak heat generation reaching up to 1.9 x 1018 W/m3, resulting in temperature as high as 352 K at the hotspot. Analysis of the results indicates that the peak temperature rise over time can be divided into three stages. The stage where the transition from strong nonequilibrium to intermediate state taking approximately 150 ps, roughly equivalent to the dissipation time of the TO2 branch, which is the primary phonon mode emitted by the hotspot with an occupancy of up to 63 %. Additionally, we examined the spatial non-equilibrium thermal transport at steady state and performed a preliminary analysis of the spatial energy dissipation process and the coupling effect between the hotspot and the interface. The research provides useful insights for further simulations of hotspot and studies of nonequilibrium thermal transport.