Date of Award
Master of Science in Nuclear Engineering
Department of Engineering Physics
John W. McClory, PhD.
AlGaN/GaN Heterostructure Field Effect Transistors (HFETs) have come under increased study in recent years due to their highly desirable material and electrical properties and survivability even during and after exposure to extreme temperature and radiation environments. In this study, unpassivated and SiN passivated Al0.27Ga0.73N/GaN HFETs were subjected to neutron radiation at 120 K. The primary focus of the research was the effects of neutron irradiation on drain current, gate leakage current, threshold voltage shift, gate-channel capacitance, and the effects of biasing the gate during irradiation. In-situ measurements were conducted on transistor current, gate-channel capacitance, and gate leakage current vs. gate bias beginning at 77 K through 300 K in 4 K temperature intervals. The drain currents increased for all devices, with a lesser increase observed for passivated devices. The changes in carrier concentration and carrier mobility, obtained from observed drain current increases and calculated with the charge control model using observed threshold voltage shifts, were attributed to trapped, positive charges in the AlGaN layer. This trapped positive charge resulted from electron-hole pairs created by neutron radiation-induced ionizations. The leakage current increased in all devices, with a smaller change observed in passivated devices. This increase was attributed to the formation of interface traps. Biasing the gate under neutron irradiation had no effect on the electrical performance of HFETs.
DTIC Accession Number
Mikina, Janusz K., "In-situ, Gate Bias Dependent Study of Neutron Irradiation Effects on AlGaN/GaN HFETs" (2010). Theses and Dissertations. 2181.