Effect of irradiation with 15-MeV protons on low frequency noise in power SiC MOSFETs

Low frequency noise is studied in 4$H$-SiC power metal-oxide-semiconductor field-effect transistors (MOSFETs) irradiated with 15-MeV protons. Irradiation is carried out at room temperature in the frequency range from 1 Hz to 50 kHz upon irradiation with doses $\Phi$ of 10$^{12}$–6 $\cdot$ 10$^{13}$ cм$^{-2}$ cm$^{-2}$. The frequency dependence of the spectral noise density $S_I$ follows the law $S_{I}\propto 1/f$ with good accuracy. A correlation between the saturation current of the output characteristic $I_d(V_d)$ and the low-frequency noise level is traced. At doses in the range 10$^{12}$ cm$^{-2}$ $\le\Phi\le$ 6 $\times$ 10$^{13}$ cm$^{-2}$, the saturation current varies within about 20%, whereas the noise level changes by two orders of magnitude. The results of noise spectroscopy are used to estimate the trap density in the gate oxide, $N_{tv}$. In unirradiated structures, $N_{tv}\approx$ 5.4 $\times$ 10$^{18}$ cm$^{-3}$ eV$^{-1}$. At $\Phi$ = 6 $\times$ 10$^{13}$ cm$^{-2}$, $N_{tv}$ increases to $\sim$7.2 $\times$ 10$^{19}$ cm$^{-3}$ eV$^{-1}$.