Approaching the Collection Limit in Hot Electron Transistors with Ambipolar Hot Carrier Transport.

Hot electron transistors (HETs) containing two-dimensional (2D) materials promise great potential in high-frequency analog and digital applications. Here, we experimentally demonstrate all-2D van der Waals (vdW) HETs formed by graphene, hBN, and WSe2, in which the polarity of carriers could be tuned by changing bias conditions. We proposed a theoretical model to distinguish hot hole and hot electron components in the ambipolar vdW HET. Importantly, both hot hole and hot electron modes are achieved with pronounced saturation behavior as well as record-high collection efficiency approaching theoretical limits (99.9%) at room temperature. The vdW HETs show a maximum output current density of 400 A/cm2. The observed ambipolar hot carrier transport with high collection efficiency is promising for high-speed nanoelectronics and 2D hot electron spectroscopy.