4H-SiC PIN Diodes as Environment to Modify 7Be Radioactive Decay Time

This work explores the possibility of using 4H-SiC PIN diodes to provide a high electric field able to induce the Stark effect in 7Be atoms implanted in the diode space charge region, modifying the 7Be radioactive decay time. A set of PIN diodes of area ranging between 2.12 × 10^−3 cm^2 and 9.88 × 10^−3 cm^2 was designed and fabricated to reach breakdown voltages up to 1000 V. Be ions were implanted in the epitaxial layer, and then the devices were reverse biased at about 75% of the theoretical breakdown voltage for durations exceeding 100 days, long enough for a precise measurement of the 7Be radioactive decay time. Electrical characterization in the pristine state, after Be ion implantation, and after long reverse bias allowed us to verify the suitability of 4H-SiC PIN diodes by assessing both the agreement between simulated and measured performance and the stability of the electric field. Be ion implantation-related defects induced both an increase in the reverse current generation and a decrease in the junction capacitance, though not affecting the breakdown voltage. Comparison with test devices implanted with the stable isotope 9Be indicates that any defects introduced by the 7Be radioactive decay are below the detection limit of the employed characterization techniques and have a negligible impact on the reverse-blocking characteristics of the diodes. Device simulations allowed us to conclude that the electric field remains close to its theoretical value throughout the experiment duration, confirming the suitability of 4H-SiC diodes for both induction and measurement of 7Be lifetime variations.