On the electron and hole tunneling in a HfO₂ gate stack with extreme interfacial-layer scaling

With decreasing SiO2 interfacial-layer (IL) thickness, gate currents in SiO2HfO2 dual-layer gate stacks are observed to undergo drastic changes. For an IL thickness below 3 AA, 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 AA;, promoting the transition in the conduction mechanism. © 2011 IEEE.