Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Department of Engineering Physics

First Advisor

Nancy C. Giles, PhD.


Silicon nitride passivation on AlGaN/GaN heterojunction devices can improve performance by reducing electron traps at the surface. This research studies the effect of displacement damage caused by 1.0 MeV electron irradiation as a function of the variation of passivation layer thickness and heterostructure layer variation on AlGaN/GaN HEMTs. The effects of passivation layer thickness are investigated at thicknesses of 0, 20, 50, and 120 nanometers on AlGaN/GaN test structures with either an AlN nucleation layer or a GaN cap structures which are then measured before and immediately after 1.0 MeV electron irradiation at fluences of 1016 cm-2. Hall system measurements are used to observe changes in mobility, carrier concentration and conductivity as a function of Si3N4 thickness. Models are developed that relate the device structure and passivation layer under 1.0 MeV radiation to the observed changes to the measured photoluminescence and deep level transient spectroscopy. A software model is developed to determine the production rate of defects from 1.0 MeV electrons that can be used for other energies and materials. The presence of either a 50 or 120 nm Si3N4 passivation layer preserves the channel current for both and appears to be optimal for radiation hardness.

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