Abstract
Combining two- and three-dimensional (2D/3D) materials provides a unique route to enabling next-generation hot electron transistors (HETs)—a vertical ballistic device, promising for high-frequency applications since they are not limited by electron velocity saturation, fabrication limitations, or short channel effects. The early demonstrations of HETs suffered from poor material and interface qualities and thick device components. The revival of the HET, with a cut-off predicted frequency above 1 THz, can be correlated with the arrival of 2D materials. Here, we discuss HET operating principles, examine HET material architectures with and without tunneling barriers, and review heterostructure considerations. We discuss material and interface properties that control barrier and base performance and critically review recent 2D/3D HETs for tunneling efficiency, output current density, current gain, and output conductance. Finally, we provide an overview of 2D and 3D semiconductors that form Schottky barriers with graphene that may be utilized as a collector while considering the device physics and growth issues.
Highlights
The terahertz (THz) spectrum, generally referred to as 100 GHz–30 THz (∼1 to 100 meV), offers unique advancements in sensing and communication applications, such as security, advanced characterization methods, cancer therapy, information, and communication technologies.[1,2] For example, THz spectroscopy will enable observation of intermolecular vibrations in various chemicals and organic molecules and low energy carrier dynamics in electronic materials not currently possible by conventional infrared (IR) spectroscopy.[1]
In graphene-based hot electron transistors (HETs) (GB-HETs), VCB leads to the injection of hot electrons into the base despite the lack of VBE due to insufficient screening by graphene.[42]
We provide a comprehensive discussion on the limitations and design considerations of the HET toward efficient electron injection, high current gain, and low output conductance, with an emphasis on GB-HETs
Summary
The terahertz (THz) spectrum, generally referred to as 100 GHz–30 THz (∼1 to 100 meV), offers unique advancements in sensing and communication applications, such as security, advanced characterization methods, cancer therapy, information, and communication technologies.[1,2] For example, THz spectroscopy will enable observation of intermolecular vibrations in various chemicals and organic molecules and low energy carrier dynamics in electronic materials not currently possible by conventional infrared (IR) spectroscopy.[1]. The arrival of 2D materials provides a route to 2D/3D HET components promising for high-frequency applications This is because of the following reasons: (1) An ultrathin E/B barrier could lead to high current injection, allowing for the fabrication of devices with a smaller area, thereby resulting in lower RC delays and higherfrequency operation of the device; (2) as long as the barrier prevents IC(leak), the use of thin B/C barriers leads to a reduction in electron–phonon scattering probability in the B/C barrier; (3) a 2D base will significantly reduce the scattering probability in the base, enabling the ballistic transport and ultra-short base transit time A double-layer tunneling barrier (TmSiO/TiO2) was utilized to prevent low energy electron injection, and a graphene/Si Schottky filtering barrier was employed
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
