Investigation of Gate Leakage Current in Nitrogen-Irradiated Al(x)Ga(1-x)N/GaN Heterostructures
AIR FORCE INSTITUTE OF TECHNOLOGY WRIGHT-PATTERSON AFB OH GRADUATE SCHOOL OF ENGINEERING AND MANAGEMENT
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Due to commercial and government interest in devices capable of functioning in high-power, high-frequency space applications, radiation tolerant AlGaNGaN devices have been under study in recent years. Passivation of the AlGaN surface by Si3N4 prevents electron trapping and enhances the 2DEG, but it also increases gate leakage currents, which can lead to device failure. This study sought information about current leakage mechanisms by introducing displacement damage close to the Si3N4AlGaN interface. The effects of irradiation damage around the Si3N4AlGaN interface on irradiation-induced leakage current were investigated for three thicknesses of a Si3N4 passivation layer in addition to an unpassivated sample. AlGaNGaN samples were irradiated at room temperature with 15-50keV nitrogen ions. Hall measurements determined mobility and 2DEG carrier density. C-V measurements provided insight into charge location and effects of the band structure. Pre-irradiation measurements were compared to the irradiation results to determine the types and amounts of damage done in the devices. Post-irradiation C-V measurements showed greater than 50 decrease in capacitance and an average -3V shift in Vth which persisted in the passivated samples. Post-irradiation Hall measurements showed decreases in mobility for both passivated and unpassivated samples. Carrier concentration decreased for passivated samples but increased for the unpassivated sample.
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