ski S. V. Influence of gamma irradiation on the reverse current-voltage characteristics of silicon photomultipliers

The study investigated the effect of Co 60 gamma-quanta on the reverse current-voltage characteristic (IV) of silicon photomultiplier (SiPMs) with 1004 cells, which themselves were optically isolated from each other n + –p–p + -structures. The cells were optically isolated from each other by trenches filled with tungsten after passivation of the walls with SiO 2 and Si3N 4 layers. Two variants of structural design of SiPMs were studied. Two variants were tested for the trench metal connection in the SiPMs: variant BI connected the trench metal to the n + -region of the cell through a quenching polysilicon resistor, while variant BII connected it to the p + -region. The breakdown voltage of the investigated SiPMs was U br = 34 ± 1.0 V. The samples were irradiated in both the active electrical mode (avalanche breakdown mode) and the passive mode (reverse bias U b = 0 V). It was discovered, that at dose of D = 10 6 rad, the dark current for SiPM (BI) and (BII) increased by 6–7 times when irradiated in passive mode and by 15–16 times for SiPM (BII) when irradiated in active mode. For SiPM (BI) irradiated in the avalanche breakdown mode, the dark current increased by 10 4 times at D = 10 5 rad. The research demonstrates that the radiation-induced degradation of the dark current in the SiPMs under study is due to an increase in the generation and, primarily, surface components. This is a result of the accumulation of positive charge in the insulating layer of the separating trenches.