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156425 https://hdl.handle.net/2286/R.I.49282 http://rightsstatements.org/vocab/InC/1.0/ All Rights Reserved 2018 xi, 109 pages : illustrations (some color) Doctoral Dissertation Academic theses Text eng McConkie, Thomas O. Smith, David J. McCartney, Martha Ponce, Fernando A. Saraniti, Marco Arizona State University Partial requirement for: Ph.D., Arizona State University, 2018 Includes bibliographical references (pages 102-109) Field of study: Physics With the high demand for faster and smaller wireless communication devices, manufacturers have been pushed to explore new materials for smaller and faster transistors. One promising class of transistors is high electron mobility transistors (HEMT). AlGaAs/GaAs HEMTs have been shown to perform well at high power and high frequencies. However, AlGaN/GaN HEMTs have been gaining more attention recently due to their comparatively higher power densities and better high frequency performance. Nevertheless, these devices have experienced truncated lifetimes. It is assumed that reducing defect densities in these materials will enable a more direct study of the failure mechanisms in these devices. In this work we present studies done to reduce interfacial oxygen at N-polar GaN/GaN interfaces, growth conditions for InAlN barrier layer, and microanalysis of a partial InAlN-based HEMT. Additionally, the depth of oxidation of an InAlN layer on a gate-less InAlN/GaN metal oxide semiconductor HEMT (MOSHEMT) was investigated. Measurements of electric fields in AlGaN/GaN HEMTs with and without field plates are also presented. Materials Science Electrical Engineering Physics 2-DEG AlGaN FIB HEMT Holography Modulation-doped field-effect transistors Gallium Nitride Investigation of Gallium Nitride Heterostructures for Application to High Electron Mobility Transistors