1Department of Information Engineering, University of Padova, 35131 Padua, Italy
Gallium Nitride-based high electron mobility transistors (HEMTs) are promising for space-based high-frequency, high-power and high-temperature electronic applications because of their high performance and resistance to total ionizing dose (TID) effects and displacement damage in typical space radiation environments. The response of GaN-based HEMT to radiation damage is a function of radiation type, dose and energy, as well as the carrier density, impurity content and dislocation density in the GaN. We review data on the radiation resistance of GaN-based devices to different types of radiation and discuss the primary degradation mechanisms. Proton and electron irradiation damage in HEMTs creates positive threshold voltage shifts due to a decrease in the two dimensional electron gas concentration resulting from electron trapping at defect sites, as well as a decrease in carrier mobility and degradation of drain current and transconductance, while 60Co γ-ray irradiation leads to much smaller changes in HEMT drain current relative to the other forms of radiation. In addition, some of the important factors that could affect the electrical characteristics after the γ-ray irradiations include the presence of a passivation layer, the metals used in the gate and Ohmic contacts, the native defect density in the barrier and GaN layers, and the gate length and gate width. Moreover, GaN-based HEMTs did not exhibit enhanced low-dose-rate sensitivity and threshold voltage shifts and transconductance degradation are larger at high dose rate than at low dose rate.
The author would like to thank Alessandro Paccagnella, Simone Gerardin, Marta Bagatin, and Chenguang Guo for patient guidance and helpful discussions.