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

Abstract

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.

There is plenty of room at the top: generation of hot charge carriers and their applications in perovskite and other semiconductor-based optoelectronic devices

“…They achieved a high on-state current density ( J c ) of 1 Acm −2 . Similarly, Liu et al recently observed ambipolar HC transport for the first time in a newly proposed device architecture of a HET transistor for the efficient collection of HC 121 . The typical device structure consists of an extra thin (~1 nm) layer by layer stacking of graphene, hexagonal boron nitride and Tungsten diselenide.…”

“…HC generation through plasmonic oscillation, especially by the interaction of LSP and the SPP, is a complex phenomenon. In a recent study, Shan et al 121 LSP and SPP that synergize to produce plasmonic HC. The electrons are excited by a 760-nm pump laser, and by crossing the Schottky barrier these electrons are injected into the MoS 2 layer where they are monitored by a probe pulse of 650 nm (Fig.…”

“…The typical device architecture consists of three terminals (emitter, base, and collector) and, under a base-to-emitter polarization condition, the hot electrons are injected from the emitter to the base region. If the base thickness is shorter than the mean free path, the hot electrons can transit through the base region without any energy loss (ballistic transport) 121 , 122 . These THz transistors rely on a channel material that can accommodate high carrier densities suitable for low-contact resistance 123 , 124 .…”

High-Frequency Graphene Base Hot-Electron Transistor

“…The bending in the base-emitter barrier is faintly lowered by the increase of V CB , causing cold electron enhancements in device I E . A similar phenomenon can be seen in the type I device, as shown in Supporting Information Figure S6a–d and is also observed in a recent research . Once the device is operated in the fixed emitter current mode, α* will not deteriorate much as V CB increases (see Supporting Information Figure S8).…”

“…This implies that the optimization of device parameters by careful selection of device materials can further improve the electrical properties of GHETs. Several studies then came after to demonstrate the use of other materials for the device’s base and insulating layers, − such as 2D transition-metal dichalcogenides or h-BN, to enhance α and increase the current density of the device. More importantly, and in addition to all these, theoretical studies have speculated that GHETs have a potential for THz frequency operations. − Since the device design employs the atomically thin graphene as the base material, injected electrons can flow ballistically through the base region, resulting in a faster transit time and better high-frequency performance.…”