Deep levels by proton and electron irradiation in 4H-SiC

The effects on 4H-silicon carbide epilayers of irradiation with protons and electrons having particle energies, respectively, of 6.5 and 8.2 MeV were carefully studied and critically compared. In detail, the electronic levels associated with the irradiation-induced defects were analyzed by current-voltage characteristics and deep-level transient spectroscopy DLTS measurements up to 550 K. In the same temperature range the apparent free-carrier concentration was measured by capacitance-voltage characteristics in order to monitor compensation effects due to the deep levels associated with the induced defects. Introduction rate, enthalpy, and capture cross section of such deep levels were compared. We found that a set of deep levels at ET=0.39 eV, ET=0.65 eV, and ET=0.75 eV is the same in both cases of proton and electron irradiations, whereas two other pairs of levels S1, ET=0.20 eV and S1*, ET=0.23 eV; S5, ET=1.09 eV and S5*, ET=0.89 eV appearing in the same temperature range within the DLTS spectra should be associated with different defect complexes according to the irradiation type. Some conclusions regarding the microscopic nature of the defects related to the deep levels have been drawn.