Design of silicon, iii-v, diamond, and graphene terafet detectors

Zhang, Yuhui
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Hella, Mona
Sawyer, Shayla
Wetzel, Christian
Shur, Michael
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Electrical engineering
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This electronic version is a licensed copy owned by Rensselaer Polytechnic Institute (RPI), Troy, NY. Copyright of original work retained by author.
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The plasmonic terahertz field-effect transistor (TeraFET) has been studied extensively since the 1990s, and has shown promise for a range of applications such as sensing, imaging, biomedical engineering, and wireless communication, owing to its high speed, low noise-equivalent power, and high tunability. Recently, TeraFETs have been identified as ideal candidates for 6G communication systems, as they exhibit excellent detection performance in the 200–500 GHz band. However, to accelerate the development and commercialization of these applications, it is essential to further enhance the sensitivity of TeraFET detectors. This thesis explores the improvement of TeraFET sensitivity using theory and verified hydrodynamic models. We compare and analyze the detection performance of TeraFETs in multiple material systems, including Si, AlGaN/GaN, AlGaAs/InGaAs, Diamond, and graphene. Our results show that p-Diamond TeraFETs have a relatively high continuous-wave (CW) response at the sub-THz band due to their high quality factor, while graphene TeraFETs are promising for pulse detection due to their low fictitious effective mass, which results in a fast response time. Additionally, electrons in graphene TeraFETs exhibit strong viscous features and possess various transport regimes. In addition to material considerations, we discuss improved TeraFET designs based on non-uniform structures. We demonstrate that using a sawtooth gate capacitance configuration can achieve a theoretically 40% increase in CW response, owing to the enhanced boundary asymmetry effects in a non-uniform geometry. Non-uniformity in TeraFETs can also be introduced by drain biasing. In a short-channel device where plasmonic oscillations reach the drain, the voltage response can be negative, indicating the amplification of incoming THz signals. This suggests that current-driven TeraFETs can be used as THz amplifiers under certain conditions. The above results provide preliminary insights into the design and optimization of TeraFETs under different operating conditions, thereby facilitating their application in various fields.
School of Engineering
Dept. of Electrical, Computer, and Systems Engineering
Rensselaer Polytechnic Institute, Troy, NY
Rensselaer Theses and Dissertations Online Collection
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