Gain Response and Ion Beam-Induced Donor Removal in nLGAD Detector: Global Gain Quenching

This study investigates the response of n-type Low Gain Avalanche Detectors (nLGADs) to local ion beam irradiation with low-penetrating 1.285 MeV gallium ions, focusing on charge collection efficiency (CCE) and gain degradation. Using the Transient Current Technique (TCT), we present charge collection maps before and after local irradiation. A 404 nm blue laser was used in postcharacterization, with no signal detected in the damaged zones after irradiation, suggesting significant charge trapping. The results reveal a pronounced vulnerability of nLGADs, with significant gain loss observed at fluences as low as 4 × 10 9 ions/cm 2. This study confirms that a donor removal mechanism occurs at low fluences, and we hypothesize that this effect is linked to vacancy-mediated mechanism. Additionally, we report a global reduction in CCE, suggesting a long-range impact on electric field triggered by local defects. This phenomenon is referred to as the global gain quenching (GGQ). Simulations of the electric field provide further confirmation of GGQ's occurrence.