Sidewall silicon carbide emitters for microfabricated Barkhausen-Kurz Terahertz vacuum electronics
- The frequency band from 300 GHz to 3.0 THz is rich in potential applications, but there is a lack of efficient sources. This "THz gap" arises from the sharp decrease in the efficiency and power output of solid-state electronic amplifiers at frequencies above 100 GHz along with the unavailability of compact, uncooled optical sources for wavelengths longer than the infrared. Future THz systems hold great promise for leveraging the unique properties of THz waves, which are long enough in wavelength to be penetrating through clothing and skin, but are short enough to be useful for imaging, are resonant with complex molecular bonds, and are low enough in energy to be safe and non-ionizing. In addition to applications in security screening and medical imaging, continuous-wave THz systems would also enable short-range extreme wideband communications. This thesis proposes a micro-fabricated Barkhausen-Kurz ([mu]-BK) oscillator as a promising candidate THz source. The Barkhausen-Kurz concept is a general electronic oscillator principle developed nearly a century ago. The [mu]-BK oscillator has significant advantages over other vacuum electronic devices, promising high DC-to-THz efficiency and low startup current requirements. This device achieves a strong coupling between the resonant cavity structure and the electron beam current, even when operated at harmonics of the electron orbit frequency, by extracting energy over multiple passes of favorably phased electrons confined within a potential well. This enables high space charge, low beam impedance, and efficient energy extraction. The need for an emitter integrated into a parabolic potential well poses a major fabrication challenge. The basic fabrication process for the cavity and integrated poly-silicon carbide thermionic cathode has been demonstrated, providing the foundation for developing stable cathodes for injecting a sheet electron beam and for optimizing the electrode geometry for defining a parabolic potential well. Thermionic emission, in contrast to field emission, has the major advantage of the decoupling the control of electron current intensity (determined by temperature) from the operating frequency (determined by electrode bias). This thesis develops the motivation for the [mu]-BK oscillator as a promising candidate for efficient integrated THz circuits. The fabrication process and results for the sidewall lateral emitter integrated into a silicon [mu]-BK cavity process are detailed. Experimental results on emission current in integrated diode test structures in vacuum are reported, that enable the design of a new vacuum electronic technology that combines electron emitters, coupled resonant cavities, and lithographically shaped electrodes in a single substrate. This new class of efficient THz vacuum electronic integrated circuits promises to bridge the THz gap.
|Type of resource
|electronic; electronic resource; remote
|1 online resource.
|Snapp, Justin Parker
|Stanford University, Department of Electrical Engineering
|Howe, Roger Thomas
|Leeson, David B
|Howe, Roger Thomas
|Leeson, David B
|Statement of responsibility
|Justin Parker Snapp.
|Submitted to the Department of Electrical Engineering.
|Thesis (Ph.D.)--Stanford University, 2012.
- © 2012 by Justin Parker Snapp
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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