Characterization and processing of semi-insulating GaN for photoconductive semiconductor switch applications

Date

2018-08

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Abstract

Photoconductive Semiconductor Switches (PCSSs) have been widely studied over the last few decades. Wide bandgap materials such as GaN are very promising for the future fabrication of PCSSs. GaN offers a great combination of electrical and optical properties such as its wide bandgap, high breakdown field, fast recombination times, and high thermal conductivity. In addition, the increasing availability of high quality crystals make this material very attractive. The goals of this thesis are to report the results of optical (cathode- and photoluminescence), structural (X-ray diffraction), morphological (scanning electron microscopy and atomic force microscopy), and electrical (two probe resistivity measurements and high voltage testing) characterization of bulk and epitaxial semi-insulating and high resistivity GaN samples grown by different methods including: Hydride vapor phase Epitaxy, Metal Organic Chemical Vapor Deposition (MOCVD), and the Ammonothermal Method. Characterization of such samples was performed to determine the best possible substrates for PCSS fabrication. These devices were fabricated using MOCVD method (low resistive contact GaN), e-beam evaporation (contact metal deposition), plasma enhanced SiO2 deposition, optical photolithography, and reactive ion plasma etching. PCSSs with various geometries were tested. Linear mode operation has been demonstrated as well as possible indications of lock-on mode switching. Future work will be needed to optimize the fabrication process and further investigate the mechanics of lock-on mode switching if GaN.

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Keywords

GaN, PCSS, Photoconductive semiconductor switches, X-ray diffraction, Scanning electron microscopy

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