Scientists Invent Hot-Emitter Transistor for Future High-Performance, Low-Power Multifunctional Devices

Transistors, the basic building blocks of integrated circuits, face increasing challenges as their size decreases. Developing transistors using new operating principles has become crucial to improving circuit performance.

Hot-carrier transistors, which exploit the excess kinetic energy of carriers, have the potential to improve the speed and functionality of transistors. However, their performance is limited by the way hot carriers are traditionally generated.

A team of researchers led by Professor Liu Chi, Professor Sun Dongming and Professor CHeng Huiming from the Institute of Metals Research (IMR), Chinese Academy of Sciences, has proposed a new hot carrier generation mechanism called stimulated emission of heated carriers (SEHC).

The team also developed an innovative hot emitter transistor (HOET), enabling an ultra-low subthreshold variation of less than 1 mV/dec and a peak-to-valley current ratio greater than 100. The study provides a prototype of a low-power, multifunctional device for the post-Moore era.

This work was published in Nature.

Low-dimensional materials such as graphene, due to their atomic thickness, excellent electrical and optical properties, and perfect surface without defects, can easily form heterostructures with other materials. This creates a variety of energy band combinations, providing new possibilities for the development of novel hot-carrier transistors.

IMR researchers have developed a hot emitter transistor using a combination of graphene and germanium, which has led to an innovative mechanism for generating hot carriers. This new transistor is composed of two coupled graphene/germanium Schottky junctions.

During operation, the germanium injects high-energy carriers into the graphene base, which then diffuse to the emitter, triggering a substantial increase in current due to the preheated carriers there. This design allows a subthreshold variation of less than 1 mV/dec, exceeding the conventional Boltzmann limit of 60 mV/dec.

At the same time, this transistor also exhibits a peak-to-valley current ratio greater than 100 at room temperature. The potential for multi-valued logic calculation has been demonstrated based on these characteristics.

“This work opens up a new field in transistor research, adding a valuable member to the hot-carrier transistor family and showing broad prospects for their application in future high-performance, low-power multifunctional devices,” Liu said.