Correlation between Defects and Electrical Performances of Ion-Irradiated 4H-SiC p-n Junctions.

In this study, 4H-SiC p-n junctions were irradiated with 700 keV He ions in the fluence range 1.0 × 10 to 1.0 × 10 ions/cm. The effects of irradiation were investigated by current-voltage (I-V) and capacitance-voltage (C-V) measurements, while deep-level transient spectroscopy (DLTS) was used to study the traps introduced by irradiation defects. Modifications of the device's electrical performances were observed after irradiation, and two fluence regimes were identified. In the low fluence range (≤10 ions/cm), I-V characteristics evidenced an increase in series resistance, which can be associated with the decrease in the dopant concentration, as also denoted by C-V measurements. In addition, the pre-exponential parameter of junction generation current increased with fluence due to the increase in point defect concentration. The main produced defect states were the Z, RD, and EH centers, whose concentrations increased with fluence. At high fluence (>10 ions/cm), I-V curves showed a strong decrease in the generation current, while DLTS evidenced a rearrangement of defects. The detailed electrical characterization of the p-n junction performed at different temperatures highlights the existence of conduction paths with peculiar electrical properties introduced by high fluence irradiation. The results suggest the formation of localized highly resistive regions (realized by agglomeration of point defects) in parallel with the main junction.