This work proposes suppression of parasitic current flow by introducing an AlGaN back barrier (BB) beneath the two-dimensional electron gas (2DEG) channel. The most suitable design, based on modelling and experimental results, is proposed. Subsequently, it was possible to compare electron mobility in the 2DEG for structures with an AlGaN BB and different dislocation densities. Experimentally, we demonstrate that reducing the dislocation density significantly increases the electron mobility in the 2DEG. Furthermore, we show that the dislocation density significantly influences the position of the Fermi level in GaN. The results presented here suggest that reducing the dislocation density could enhance the performance of high-frequency GaN HEMT applications.
