AlGaN/GaN field effect transistors for power electronics: Effect of finite GaN layer thickness on thermal characteristics

AlGaN/GaN heterostructure field effect transistors with a 150 nm thick GaN channel within stacked Al xGa1−xN layers were investigated using Raman thermography. By fitting a thermal simulation to the measured temperatures, the thermal conductivity of the GaN channel was determined to be 60 W m−1 K−1, over 50% less than typical GaN epilayers, causing an increased peak channel temperature. This agrees with a nanoscale model. A low thermal conductivity AlGaN buffer means the GaN spreads heat; its properties are important for device thermal characteristics. When designing power devices with thin GaN layers, as well as electrical considerations, the reduced channel thermal conductivity must be considered.