A hot-emitter transistor based on stimulated emission of heated carriers.

Hot-carrier transistors are a class of devices that leverage the excess kinetic energy of carriers. Unlike regular transistors, which rely on steady-state carrier transport, hot-carrier transistors modulate carriers to high-energy states, resulting in enhanced device speed and functionality. These characteristics are essential for applications that demand rapid switching and high-frequency operations, such as advanced telecommunications and cutting-edge computing technologies1-5. However, the traditional mechanisms of hot-carrier generation are either carrier injection6-11 or acceleration12,13, which limit device performance in terms of power consumption and negative differential resistance14-17. Mixed-dimensional devices, which combine bulk and low-dimensional materials, can offer different mechanisms for hot-carrier generation by leveraging the diverse potential barriers formed by energy-band combinations18-21. Here we report a hot-emitter transistor based on double mixed-dimensional graphene/germanium Schottky junctions that uses stimulated emission of heated carriers to achieve a subthreshold swing lower than 1 millivolt per decade beyond the Boltzmann limit and a negative differential resistance with a peak-to-valley current ratio greater than 100 at room temperature. Multi-valued logic with a high inverter gain and reconfigurable logic states are further demonstrated. This work reports a multifunctional hot-emitter transistor with significant potential for low-power and negative-differential-resistance applications, marking a promising advancement for the post-Moore era.

Flexible 64 × 64 Pixel AMOLED Displays Driven by Uniform Carbon Nanotube Thin-Film Transistors.

Carbon nanotube (CNT) thin-film transistors are expected to be promising for use in flexible electronics including flexible and transparent integrated circuits and in wearable chemical and physical sensors and for driving the circuits of flexible display panels. However, current devices based on CNT channels suffer from poor performance uniformity and low manufacturing yield; therefore, they are still far from being practical. This is usually caused by nonuniform deposition of the semiconducting CNTs and the rough surface of flexible substrates. Here, we report CNT thin-film transistors (TFTs) driving a flexible 64 × 64 pixel active matrix light-emitting diode display (AMOLED) by improving the formation of uniform CNT films and developing a new pretreatment technique for flexible substrates. The achieved AMOLED has uniform brightness and a high yield of 99.93% in its 4096 pixels. More than 8000 TFTs with high-purity semiconducting CNTs as the channel material show an average on-off current ratio of ∼107 and a carrier mobility of 16 cm2 V-1 s-1. The standard deviations of the on-state current and the carrier mobility are 4.1 and 6.5%, respectively. Our result shows that the panel driven by high-purity semiconducting CNTs is a promising strategy for the development of next-generation flexible, large-area displays.

Tailoring of electromagnetic field localizations by two-dimensional graphene nanostructures.

Graphene has great potential for enhancing light-matter interactions in a two-dimensional regime due to surface plasmons with low loss and strong light confinement. Further utilization of graphene in nanophotonics relies on the precise control of light localization properties. Here, we demonstrate the tailoring of electromagnetic field localizations in the mid-infrared region by precisely shaping the graphene into nanostructures with different geometries. We generalize the phenomenological cavity model and employ nanoimaging techniques to quantitatively calculate and experimentally visualize the two-dimensional electromagnetic field distributions within the nanostructures, which indicate that the electromagnetic field can be shaped into specific patterns depending on the shapes and sizes of the nanostructures. Furthermore, we show that the light localization performance can be further improved by reducing the sizes of the nanostructures, where a lateral confinement of λ0/180 of the incidence light can be achieved. The electromagnetic field localizations within a nanostructure with a specific geometry can also be modulated by chemical doping. Our strategies can, in principle, be generalized to other two-dimensional materials, therefore providing new degrees of freedom for designing nanophotonic components capable of tailoring two-dimensional light confinement over a broad wavelength range.

A review of carbon nanotube- and graphene-based flexible thin-film transistors.

Carbon nanotubes (CNTs) and graphene have attracted great attention for numerous applications for future flexible electronics, owing to their supreme properties including exceptionally high electronic conductivity and mechanical strength. Here, the progress of CNT- and graphene-based flexible thin-film transistors from material preparation, device fabrication techniques to transistor performance control is reviewed. State-of-the-art fabrication techniques of thin-film transistors are divided into three categories: solid-phase, liquid-phase, and gas-phase techniques, and possible scale-up approaches to achieve realistic production of flexible nanocarbon-based transistors are discussed. In particular, the recent progress in flexible all-carbon nanomaterial transistor research is highlighted, and this all-carbon strategy opens up a perspective to realize extremely flexible, stretchable, and transparent electronics with a relatively low-cost and fast fabrication technique, compared to traditional rigid silicon, metal and metal oxide electronics.