EAGER: A Novel GaN/AlGaN Nanostructure Room-Temperature Sensor for Security Applications

George Mason University, Fairfax VA

Investigators

Abstract

Overview: In recent years terahertz technology has gained significant interest, as the terahertz rays are non-ionizing and have appealing applications in security screening, homeland security, radio astronomy, manufacturing, communication and bio-sensing. The proposed research will demonstrate the viability of GaN/AlGaN core/shell nanostructure based multi-channel field-effect transistor (FET) arrays for sensing of Terahertz (THz) radiation in the range 0.5 to 5 THz using plasmonic excitations of the two-dimensional electron gas in such structures. By using novel design and fabrication strategies, high electron gas density with improved plasma wave velocities and frequencies are feasible, which will ensure the operation of these detectors at room temperature. The broad reaching goals of this basic research are two-fold: 1) to observe resonant detection with good quality factor with frequency tunability at room temperature and 2) to develop a design strategy for demonstrating radially-confined two-dimensional Plasmon filters for detecting radiation over a selected bandwidth. The objective of this project is to realize GaN/AlGaN nanostructure based heterojunction multi-channel FET detector arrays, to provide good detection responsivity in the frequency range of 0.5-5 THz, and study their performance at room temperature. Suspended GaN nanostructure (core) arrays will be formed by using electron beam lithography and plasma-etch techniques on epilayers of GaN on Si substrate. AlGaN shells will be grown on the GaN cores to form core/shell heterojunction nanostructures. Realization of nanostructure FETs with dimensionally confined carrier plasma for THz detection is the goal of this EAGER proposal. Physical attributes of the hetero-junction will be varied to tune the device performance. Coupling of the radiation with different antenna geometries will also be investigated. The characterization of detector array FETs includes measurements to establish figure of merits like responsivity and noise equivalent power (NEP). Intellectual Merit : The project's intellectual merit centers on the challenges and opportunities offered by the large-scale arrayed architecture of novel core/shell nanostructure multi-channel FET device design. This project will advance our understanding of the interactions of THz radiation with radially-confined electron gases in nanoscale structures. Detection in the THz frequency regime at room temperature can be realized by exploiting the property of high electron gas density at the GaN/AlGaN interface and the improved plasma wave velocities and frequencies by the use of nanoscale device architectures. The research will demonstrate electronically-tunable THz detection by the use of wrapped gate architectures (for better voltage control). This study would address the fundamental question if the geometrically confined carrier plasma enable high performance tunable THz detection at room temperatures. This study will investigate the effect of the various core/shell nanostructure device parameters and antenna structures on the detector performance. This research aims to establish a new paradigm for core/shell nanostructure based THz detection devices. Broader Impacts: Successful completion of this project will advance our understanding of the THz interaction with the novel nanostructure core/shell device architectures for improved detector performance at room temperature. Results of this project will also have a significant effect on the development of high-performance nitride-based heterojunction nanostructure FET arrays for integration in focal plane arrays (FPA). Such FPAs can be used in real time THz imaging for cancer detection, and homeland security and defense applications. A graduate student will get hands-on experience in a state of the art nanofabrication facility at NIST. Results of this work will be integrated into a graduate level course in the electronics track at GMU. High school students will work on the project during summer.