Thermo-mechanical aspects of gamma irradiation effects on GaN HEMTs

We report thermal and mechanical responses accompanying electrical characteristics of depletion mode GaN high electron mobility transistors exposed to gamma radiation up 107 rads. Changes in the lattice strain temperature were simultaneously characterized by changes phonon frequency E2 (high) A1 (LO) from on-state unpowered/pinched off reference states. Lower doses improved properties; however, degradation initiated at about 106 observed 16% decrease saturation current 6% transconductance highest dose. However, a leakage increase three orders magnitude was most notable effect. 40% stress factor dose rads compared pristine devices. Spatial mapping along channel identifies gate region as mechanically affected area, whereas mostly uniform. Transmission microscopy showed contrast reflecting vacancy concentration region. These findings suggest that localized (mechanical hotspots) may vulnerability damage accommodating higher defects promote current.