The Impact of Nongray Thermal Transport on the Temperature of AlGaN/GaN HFETs

The hotspot temperature in AlGaN/GaN heterostructure FETs has been of great interest due to its effect on the reliability of these devices. Both the nanoscale heat transfer effects and complex energy transfer mechanism from electrons to lattice are factors affecting the hotspot temperature, which is not accounted for in continuum level thermal simulations. The effects of heat generation zone size and the energy transfer mechanism from electrons to the lattice on the hotspot temperature were analyzed using electrical and nongray ballistic-diffusive thermal transport simulations for devices operated at a fixed power, but different biasing conditions. Results show that hotspot temperatures are impacted from nanoscale effects but the complex energy scattering mechanisms from electrons to the lattice do not have a significant impact on the hotspot temperature due to the scattering and redistribution of the energy within the phonon population.