Thermally stimulated capacitance in gamma irradiated epitaxial 4H-SiC Schottky barrier diodes

Deep level defects in 4H-SiC Schottky barrier diodes (SBDs) fabricated on n-type epitaxial 4H-SiC have been identified by thermally stimulated capacitance (TSCAP) spectroscopy prior to and after ⁶⁰Co-gamma irradiation. The TSCAP measurements on the non-irradiated SBDs reveal two electron traps at E_c-0.63 eV (∼250 K) and E_c-1.13 eV (∼525 K), whereas only one trap at E_c-0.63 eV is identified by conventional thermally stimulated current (TSC) measurements. Hence, TSCAP spectroscopy is more effective in identifying deep level defects in epitaxial 4 H-SiC SBDs as compared to the TSC spectroscopy. Upon exposure to ⁶⁰Co-gamma rays up to a dose of 100 Mrad, significant changes in the concentration of the traps at E_c-0.63 eV, E_c-1.13 eV, and one new trap at E_c-0.89 eV (∼420 K) are observed. The electrical characteristics of the SBDs are considerably changed after gamma irradiation. The dominant mechanisms responsible for the irradiation induced changes in the SBD electrical characteristics are analyzed by incorporating the trap signatures in the commercial Silvaco^® TCAD device simulator. The extracted trap parameters of the irradiated SBDs may be helpful in predicting the survival of 4H-SiC SBD detectors at higher irradiation levels.