Enhancement of breakdown characteristics of AlGaN|GaN HEMT with back barrier plus high-$k$ passivation layer

In this article, a novel breakdown enhanced AlGaN|GaN high electron mobility transistor (HEMT) with the architecture of AlGaN back barrier and high-$k$ passivation layer is investigated by numerical simulation. It is indicated that the off-state voltage of AlGaN|GaN HEMT has increased significantly by inducing the AlGaN back barrier and high-$k$ passivation layer. The breakdown voltage of device has increased by 90.1%, to 616 from 324 V, with a 50-nm high-$k$ passivation layer and 100-nm Al$_{0.05}$Ga$_{0.95}$N back-barrier layer. This is mainly due to that the electric field at the drain gate zone is modulated by high-$k$ passivation layer and becomes smaller in the gate corner. Moreover, the buffer leakage current got effectively reduced due to the introduction of the back-barrier layer, which could also improve the breakdown voltage of the device. In addition, the results also show that the channel current IDS of the device is slightly increased by the back-barrier + passivation structure, while the frequency performance shows no obvious degradation. Simulation results suggest that the AlGaN back barrier plus high-$k$ passivation layer can effectively improve the breakdown voltage of the device without sacrificing the characteristics of the device.