Role of shallow surface traps and polarization charges in nitride-based passivation for AlGaN/GaN heterojunction FET

In this work, we investigated the mechanisms of nitride-based passivation (i.e. SiNx and AlN) and their impact on high-voltage switching of AlGaN/GaN heterojunction power transistors with TCAD simulations. It was found that they play a vital role for nitride-passivated devices to simultaneously achieve low dynamic ON-resistance (Ron) and uncompromised breakdown capability. Simulated 2-D electrostatic OFF-state potential distributions and RON transients after switching suggested that the polarization charges together with fast-response shallow traps situated at the passivation/gap interface would improve the dynamic RON stability and at the same time effectively lower electric fields at the drain-side gate edge. The difference between SiNx and AlN as surface passivant for GaN HEMTs were also analyzed.