Channel Temperature Analysis of GaN HEMTs With Nonlinear Thermal Conductivity

This paper presents an enhanced, closed-form expression for the thermal resistance, and thus, the channel temperature of AlGaN/gallium nitride (GaN) HEMTs, including the effect of the temperature-dependent thermal conductivity of GaN and SiC or Si substrates. In addition, the expression accounts for temperature increase across the die-attach. The model's validity is verified by comparing it with experimental observations. The model results also compare favorably with those from finite-element numerical simulations across the various device geometric and material parameters. The model provides a more accurate channel temperature than that from a constant thermal conductivity assumption; this is particularly significant for GaN/Si HEMTs where the temperature rise is higher than in GaN/SiC. The model is especially useful for device and monolithic microwave integrated circuit designers in the thermal assessment of their device design iterations against required performance for their specific applications.