The Thermal Response of Gallium Nitride HFET Devices Grown on Silicon and SiC Substrates

Abstract

In this study a multi-scale thermal approach is presented and used for the prediction of the hotspot temperature of AlGaN/GaN Heterojunction Field Effect Transistors(HFETs) grown on Si and SiC substrates. The multi-scale approach accounts for heat generation within the device obtained using Sentaurus Device Simulator. The heat generation regions within the device were found to be highly localized to nanometer sized domains. Heat transfer modeling in the small heat generation region was performed by solving the gray phonon BTE to capture the ballistic-diffusive nature of phonon transport. This model was coupled to a diffusive thermal transport finite element code (COMSOL) to extend the device domain and obtain the thermal boundary conditions for the smaller BTE domain. The calculated hotspot temperatures under different biasing conditions were compared for devices grown on Si/SiC substrates. The impact of the heat dissipation path and methods to reduce hot spot temperature are discussed.