Engineering Commons^™

Study Of 4h-Sic And Alxga1-Xn Based Heterojunction Devices For Ultraviolet Detection Applications, Venkata Surya Naga Raju Chava

Theses and Dissertations

Ultraviolet (UV) detectors are important for their applications in flame detection, furnace gas control systems, plume monitoring etc. Due to their wide band-gap, 4H-SiC (Eg=3.26eV) and III-V semiconductors such as GaN (Eg=3.4eV), AlxGa1-xN (Eg=3.4eV to 6.2eV) etc., are excellent candidates for visible(��cut-0ff=400nm) and solar blind(��cut-0ff=290nm) UV detectors. Conventional SiC UV detectors suffer from poor UV responsivities due to reflection/absorption/transmission losses caused by the metal electrodes used in those detectors.

In the first part, a novel bipolar transistor with epitaxial graphene(EG)/p-SiC (30μm)/n+-SiC substrate was fabricated and characterized. The 2-3 ML thick, transparent and conducting, EG used in this work was grown …

High Resolution Radiation Detectors Based On 4h-Sic N-Type Epitaxial Layers And Pixilated Cdznte Single Crystal Devices, Cihan Oner

Theses and Dissertations

Silicon Carbide (SiC) is an indirect wide bandgap semiconductor with high thermal conductivity, high breakdown electric field, high carrier saturation drift velocity, and large displacement energy making it a suitable candidate for replacing conventional radiation detectors based on Si, Ge, CdTe, and CdZnTe (CZT). In this dissertation, fabrication and characterization of high-resolution Schottky barrier detectors for alpha particles using 20 µm thick n-type 4H-SiC epitaxial layers are reported. Schottky barriers were obtained by depositing circular nickel contacts of ~10 mm2 area.

Room temperature current-voltage (I-V) measurements revealed Schottky barrier heights of the order of 1.7 eV, ideality factor of ~1.1, …

Novel Wideband Ebg Structures For Isolation Improvement Between Cosite Antennas, Paul John Czeresko Iii

Theses and Dissertations

As the number of installed antennas increases on a structure, the available real estate to do so without each antenna interfering with the others diminishes. Electromagnetic band gap (EBG) structures are one way to mitigate this cosite interference with compact antenna installations. While a host of EBG structures and types (3-D, planar etc.) have been proposed and studied historically, it has been found that planar EBG structures tend to provide very narrow bandwidths for both antenna design and cosite interference reduction. This research focuses on the design of EBG structures intended to achieve greater than 20 dB of isolation improvement …

Structurally Integrated Reconfigurable Wideband Array For Conformal Applications, Michael Damon Wright

Theses and Dissertations

Structurally integrated conformal antennas offer significant advantages over traditional bolt on antennas, especially for air vehicle applications. The ability to leverage the entire structure allows for unconventionally large antennas and arrays to be implemented in a manner which does not detract from the aerodynamic, structural or aesthetic qualities of the vehicle. Works along this line have included Slotted Waveguide Antenna Stiffened Structures (SWASS), conformal helix and spiral antennas, Log Periodic Dipole Arrays (LPDA), and other antennas.

An area which has not been investigated to date is the possibility of implementing reconfigurable antennas in a structural environment. There are inherent challenges …

Multifunction Radio Frequency Composite Structures, David L. Zeppettella

Theses and Dissertations

There has been recent interest in the development of multifunction structures for weight-critical applications. A multifunction structure is a load-bearing structure that also allows one or more additional functions such as RF communication, energy storage, sensing etc. The focus of this dissertation is to analyze, design, develop, and test new high performance (broadband, high gain, circularly polarized) internal antennas that are structural and integral to the aircraft. It is demonstrated that antennas with more bandwidth and higher efficiency could be developed if the space and materials available in an aircraft structure could be judiciously exploited for multifunctional usage. This is …