Radio-frequency (RF) switches using Field-Effect Transistors (FETs) have low loss, fast switching speed, and simple fabrication process, which allows for simple integration with other components such as power amplifiers, phase shifters arrays, etc. Recent advancements in III-nitride heterostructure field-effect transistors (HFET) have led to RF switches with outstandingly low loss and high power handling capability, ideal for numerous applications. However, relatively high ohmic contact resistivity, large OFF-state capacitance, and diddiculty in gate alignment limit HFET's application for RF switching to frequencies not exceeding 6 GHz. In this dissertation, a new type of gateless microwave switch using capacitively-coupled contact (C 3) is presented, which operates under very different mechanism than conventional ohmic HFET, and has lower loss, smaller OFF-state capacitance, and better high power capability at frequencies exceeding 10 GHz, as well as the privilege of self-aligned fabrication process. To fully demonstrate the capability of this new device type, a novel design of MMIC traveling-wave switch using proposed gateless device is presented, with sub 1 dB insertion loss and above 40 dB isolation measured on-wafer at 12–20 GHz, as well as more than +40 dBm power handling capability. To the author's best knowledge, it is up-to-date the best performance of III-N switch ever reported. A conceptual design for even higher frequency range is also presented, which functions at 30–70 GHz with same performance based on realistic numerical simulation.
|Commitee:||Ali, Mohammod, Koley, Goutam, Li, Xiaodong|
|School:||University of South Carolina|
|School Location:||United States -- South Carolina|
|Source:||DAI-B 71/05, Dissertation Abstracts International|
|Keywords:||Capacitively-coupled contact, Gallium nitride, Gateless, HFET, Microwave switches, Traveling-wave concept|
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