Capacitance–conductance characteristics of PMI-based MIS Schottky diodes under high-dose gamma irradiation and ambient ageing

Au/perylene-monoimide (PMI)/n-Si/In metal–insulator–semiconductor (MIS) Schottky diodes were fabricated by spin coating a thin (∼16 nm) PMI organic interfacial layer on a chemically cleaned n-type Si (100) substrate. The capacitance–voltage (C–V) and conductance–voltage (G–V) characteristics of the diodes were measured at 1 MHz at room temperature, before and after exposure to 20, 40 and 80 kGy 60Co γ-ray doses, and again after 2, 7, 30 and 60 d of post-irradiation room-temperature ageing of the 80 kGy device. The series resistance (Formula presented) (Formula presented) was extracted from the high-frequency conductance technique and used to recover the corrected capacitance (Cc) and parallel conductance ( (Formula presented) (Formula presented) ). Diode parameters—donor concentration ( (Formula presented) (Formula presented) ), diffusion potential ( (Formula presented) (Formula presented) ), depletion width ( (Formula presented) (Formula presented) ), image-force barrier lowering (Formula presented) (Formula presented) and barrier height (Formula presented) (Formula presented) —were determined from the linear part of the (Formula presented) (Formula presented) plot. The interface state density ( (Formula presented) (Formula presented) ) at the peak of the (Formula presented) (Formula presented) curves was obtained by the Hill–Coleman single-frequency method. With increasing γ-dose (Formula presented) (Formula presented) decreases from 5.40 × 1015 to 2.81 × 1015 cm−3, (Formula presented) (Formula presented) drops from 0.963 to 0.899 eV, the depletion layer widens from 430 to 561 nm and the peak (Formula presented) (Formula presented) increases from 57.1 to 70.8 Ω, while (Formula presented) (Formula presented) exhibits a strongly non-monotonic, dose-dependent behaviour. Post-irradiation ageing partially restores all parameters: (Formula presented) (Formula presented), (Formula presented) (Formula presented) and (Formula presented) (Formula presented) return towards their pre-irradiation values, and (Formula presented) (Formula presented) decreases by almost three orders of magnitude during the first week before stabilising. The results indicate that PMI-based MIS Schottky structures undergo significant irradiation-induced electrical modifications but attain a relatively stable and partially self-passivated state after (Formula presented) (Formula presented) 30 d of room-temperature ageing, indicating that the Au/PMI/n-Si/In structure retains measurable electrical functionality after high-dose γ-irradiation and may warrant further investigation for radiation-tolerant electronic applications.