On the Electron and Hole Tunneling in a $\hbox {HfO}_{2}$ Gate Stack With Extreme Interfacial-Layer Scaling

With decreasing SiO₂ interfacial-layer (IL) thickness, gate currents in SiO₂/HfO₂ dual-layer gate stacks are observed to undergo drastic changes. For an IL thickness below 3 Å, a transition from hole-current-dominated transport to electron-current-dominated transport is observed near operating bias conditions in p-channel field-effect transistors. A tunneling simulation based on the transfer-matrix approach suggests that the band offsets for the SiO₂ and HfO₂ layers are reduced in the submonolayer IL regime ( <; 3 Å), promoting the transition in the conduction mechanism.