Improved RF power performance in GaN-on-SiC HEMTs through thermal design of the GaN buffer layer

Abstract

This study investigates the thermal dissipation capability and electrical performance of GaN-on-SiC high electron mobility transistors (HEMTs) through the thermal design of the GaN epilayer. The Debye–Callaway model was employed to analyze the relationship between impurity concentrations, GaN thickness, and GaN thermal conductivity. An optimized Fe/C co-doped buffer design was proposed to mitigate the effect of Fe impurities on thermal conduction within GaN epilayers. The thermal conductivity of the GaN epilayer was extracted through transducer-less transient thermoreflectance, which was improved by 40 W/m K compared to the reference structure, resulting in a 25 °C reduction in device peak temperature at a dissipated power density of 10 W/mm. Consequently, the output power density of the GaN HEMTs with the designed Fe/C co-doped buffer was improved from 16.4 to 19.1 W/mm, and the power added efficiency increased from 48.0% to 52.3% at 3.6 GHz under Vd = 70 V, illustrating the critical role of the thermal design for the GaN epilayer in advancing the RF power performance of GaN-based HEMTs.