(Non-Technical) The goal of this project is to develop a new generation of electronic devices capable of efficiently operating at frequencies well above those attainable in current state-of-the-art electronic devices, into the terahertz region of the spectrum. Over the past decade, the terahertz frequency regime, the region of the electromagnetic spectrum located between the microwave and the infra-red, has become the subject of much attention due to its wide range of unique applications in diverse areas such as astronomy, imaging, spectroscopy, security, communications, and so on. Although significant progress has been recently achieved, there is still a need for devices efficiently operating at these frequencies. In particular, there is a necessity for low-cost, compact sources of terahertz radiation. In this context, the research targeted in this proposal tries to provide an answer for a long standing problem for the terahertz community: how to achieve power gain at terahertz frequencies in compact, electronic devices at room-temperature. The proposed devices can offer low cost of manufacturing, and therefore will find many potential industrial applications in future compact terahertz systems (e.g. "terahertz chips" for communications, security, and biomedical applications). This research vision is interlaced with an educational vision of mentoring new generations of graduate and undergraduate students in the field of materials, high frequency electronics, terahertz, and optics and stimulating their critical thinking and curiosity by providing them with hands-on experience in cutting-edge research. This is of significant importance given the future projected needs for highly trained engineers and scientists in the United States, and in particular in the state of Utah. The proposed research and educational plans will leverage the ongoing research activities on materials, electronics and optoelectronics and the current outreach programs at the University of Utah.
(Technical) This project aims to develop active terahertz electronic devices (terahertz detectors, oscillators, and amplifiers) based on the interplay between resonant tunneling and electron plasma waves in stacked two-dimensional material layers. These devices promise power gains >7dB at frequencies above 2 THz when in amplifier configurations, which has been proven to be difficult to achieve in traditional high-frequency electronic-devices. The fundamental mechanism enabling gain at terahertz frequencies in these devices is the interplay between negative differential conductance (NDC) and the electron plasma waves in a two-dimensional electron gas (2DEG), i.e. the NDC provides a gain medium for the plasma waves excited in the semiconductor 2DEG. All the challenges associated with these devices are going to be identified and addressed at the materials, device fabrication, and design stages. Of these 2D materials, graphene, can be an excellent platform for plasmonic transport owed to its large room temperature mobility thus low plasmonic damping. Moreover, its intrinsic 2D nature, and its ease of transfer to arbitrary substrates can allow for unlimited degrees of freedom of integration, reduce the cost with respect to that in III-V semiconductors, and allow for more simple fabrication processes. We will also answer questions regarding high quality 2D material preparation: control and optimization of domain size, integrity, inclusions, interface boundaries, contamination, fidelity of crystallography / alignment between stacked layers, and terminating carbon bonding.
