Multiscale Modeling of Hot Spots in GaN High Electron Mobility Transistors

A coupled Lattice Boltzmann (LB)-Finite Difference (FD) method is used to solve for the heat transport in a 6 finger GaN high electron mobility transistor. The LB method is used to capture relevant phonon physics near a microscopic heat generation region by solving the Boltzmann Transport Equation, while an FD model is used to capture the thermal transport at the macroscopic level. The coupling region between the LB and FD domains, which enables multiscale modeling, is discussed. The results of the multiscale models were compared to results generated from other numerical methods. An increasing departure from diffusion theory is observed with increasing dissipated power under the gray phonon model. This difference is attributed to a combination of boundary scattering effects as well as phonon confinement within the small dimensions of the hot spot.