Investigation of Electrical Performance Degradation and Trap States in Depletion-Mode Metal-Insulator-Semiconductor (MIS) GaN HEMTs Under Heavy Ion Irradiation

This study investigates the electrical performance degradation of metal-insulator-semiconductor GaN high electron mobility transistors (MIS-HEMTs) subjected to high-energy tantalum ion irradiation, focusing particularly threshold voltage (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$V$</tex><inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</inf>) characteristics within the device. Following heavy ion irradiation, the device exhibits a reduction in single-event burnout voltage, a positive <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$V$</tex><inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</inf> shift of 0.65 V, and a 31.5% reduction in saturated output current. Through temperature-dependent transfer and gate leakage analyses, and numerical simulations, it is determined that the localized trap states in the MIS gate region are primarily responsible for the observed electrical performance degradation. The corresponding trap state density is evaluated, which is an order of magnitude higher than that of the unirradiated device. Furthermore, the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$V$</tex><inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</inf> behavior of the irradiated device under long-term electrothermal stress conditions is evaluated, with an activation energy as determined from temperature-dependent measurements. These findings offer valuable insights into the mechanisms underlying electrical performance degradation and provide critical guidance for future hardening strategies in MIS-GaN HEMTs exposed to extreme radiation environments.