Toward high-current-density and high-frequency graphene resonant tunneling transistors
Zihao Zhang, Baoqing Zhang, Yifei Zhang, Yiming Wang, Patrick Hays, Sefaattin Tongay, Mingyang Wang, Hecheng Han, Hu Li, Jiawei Zhang, Aimin Song
Abstract
Abstract Negative differential resistance (NDR), a peculiar electrical property in which current decreases with increasing voltage, is highly desirable for multivalued logic gates, memory devices, and oscillators. Recently, 2D quantum-tunneling NDR devices have attracted considerable attention because of the inherent atomically flat and dangling-bond-free surfaces of 2D materials. However, the low current density of 2D NDR devices limits their operating frequency to less than 2 MHz. In this study, graphene/hexagonal boron nitride (h-BN)/graphene resonant tunneling transistors (RTTs) were fabricated using graphene and h-BN barriers with different numbers of atomic layers, showing a mechanism enabling the observation of NDR in high current density devices. A triangular etching approach was proposed to suppress the effects of graphene–metal contact resistance and graphene sheet resistance, enabling pronounced NDR effect even in a 2D tunneling device with a single atomic layer h-BN barrier. A room-temperature peak current density up to 2700 μA/μm 2 and operational frequencies up to 11 GHz were achieved, demonstrating the potential of 2D quantum NDR devices for applications in high-speed electronics.