Experimental Evidence of the Effect of Ionizing Radiation on the Space Charge Region in BJTs

ABSTRACT This study investigates the interplay between ionizing radiation‐induced interface traps and displacement defects in NPN bipolar junction transistors (BJTs) containing high‐density Au defects. Through 60 Co γ‐ray irradiation experiments and technology computer‐aided design (TCAD) simulations, we demonstrate that positively charged interface traps induce a spatial redistribution of the space charge region (SCR), contracting the SCR in the N‐type collector while expanding it into the P‐type base. Deep‐level transient spectroscopy (DLTS) reveals a 40% reduction in Au defect concentration (from 1.09 × 10 14 cm −3 to 6.55 × 10 13 cm −3 ) post‐irradiation, corroborated by simulated electron concentration profiles. These findings provide direct experimental evidence of ionizing radiation's impact on SCR modulation, critical for radiation‐hardened device design.