Advancing Low-Voltage Complementary Reconfigurable Field-Effect Transistor Operation with Reduced Schottky Barriers

The reconfigurable field-effect transistor (RFET) can exhibit both n-type and p-type transistor functionalities simultaneously [1] , offering enhanced flexibility in circuit design. At the expense of increased device size due to additional gates, multiple functions can be integrated within the same footprint, or equivalent functionality can be achieved with fewer device counts, and improved flexibility of adjusting drive strength by the additional gates. Despite considerable efforts in exploring RFETs, their low saturation current (I ON ) remains a significant hurdle, limiting their application in high-performance circuits. Since the operation of RFETs relies on the Schottky tunneling process occurring at the source/drain (S/D) contacts, increasing tunneling probability is considered a method to enhance I ON . In most cases, nickel-silicide (NiSi) is used as a contact material exhibiting Schottky Barrier Height (SBH) of approximately 0.56eV for both types [2] ; thereby, the elevated SBHs render it unfeasible to achieve high tunneling probability at lower operating voltages. To address the challenge, we propose RFET topologies that can improve for n-type and p-type operations operating at lower voltages, leveraging SenTaurus Technology Computer-Aided Design (TCAD) simulations [3] . The n-type enhanced RFET (NRFET) features a titanium (Ti)/zinc-oxide (ZnO)/heavily doped n-type silicon (n + -Si) S/D structure [4] to reduce contact resistivity (ρ c ) by alleviating Fermi-level pinning. In contrast, the p-type enhanced RFET (PRFET) adopts a titanium (Ti)/heavily doped p-type silicon (p + -Si) S/D structure, allowing for a reduction of the SBH and an induction of doping-induced band bending. Also, we propose a multi-bridge channel FET (MBCFET) [5] based complementary RFET (CRFET) by stacking one device on top of another that functions as both types.