Enhanced Reliability of Ferroelectric GaN HEMTs With Reduced Depolarization-Field Effect

In this study, we investigate depolarization- field effect of an AlGaN barrier layer on ferroelectric GaN HEMTs with an AlScN/HfO2 gate stack (FeHEMT). Both recessed and non-recessed gate structures are fabricated and characterized not only to compare memory window and threshold voltage tunability but also analyze the depolarization-field effect on cycling and endurance properties. Fast ramped pulse I-V measurements reveal the difference between the two structures by excluding the ferroelectric polarization switching of the AlScN layer. Superior ferroelectric switching properties are achieved and maintained due to the reduced AlGaN layer. The recessed-gate FeHEMT is promising for GaN-based emerging memory and neuromorphic devices.