Background Avalanche transistors are extensively employed in microwave devices, pulse power supplies, and various other applications. Owing to their capability of generating instantaneous high power, significant thermal management challenges arise. The active region of an avalanche transistor operates at the micrometer scale, where classical Fourier's law of heat conduction becomes inadequate due to the breakdown of phonon diffusive transport assumptions. At such microscopic dimensions, the heat transfer mechanism deviates markedly from that at macroscopic dimensions. The Boltzmann Transport Equation (BTE) of phonon scattering, which remains valid across multiple spatiotemporal scales, provides a robust framework for modeling non-Fourier thermal transport phenomena.

Purpose This study aims to propose a new electrothermal coupling method for simulating the working process semiconductor devices, in order to capture the non-Fourier heat conduction effect within semiconductor materials at the micro-nanoscale, where phonon ballistic transport dominates.

Methods In this study, the phonon BTE is adopted as the governing equation, and the Lattice-Boltzmann Method (LBM) is employed for spatial and temporal discretization to establish a mesoscopic numerical model of non-Fourier heat conduction at the microscale. This model is applied to simulate the transient thermal behavior of avalanche transistors, with input conditions derived from TCAD-based electrothermal coupling simulations.

Results The internal temperature field of the avalanche transistor predicted by the non-Fourier conduction model is higher than that of the traditional Fourier conduction model.

Conclusions These findings highlight the importance of incorporating non-Fourier heat conduction effect into the thermal analysis of micro-nano scale devices.