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. SiN x 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 R ON transients after switching suggested that the polarization charges together with fast-response shallow traps situated at the passivation/gap interface would improve the dynamic R ON stability and at the same time effectively lower electric fields at the drain-side gate edge. The difference between SiN x and AlN as surface passivant for GaN HEMTs were also analyzed.