Electrical and noise properties of proton irradiated 4H-SiC Schottky diodes.

The current voltage characteristics and the low-frequency noise in high voltage 4H-SiC junction barrier Schottky diodes irradiated with high energy (15MeV) protons were studied at different temperatures and irradiation doses Φ from 3 x 10¹² cm^-2 to 1 x 10¹⁴ cm^-2. Irradiation led to the increase of the base resistance and the appearance of slow relaxation processes at small, V ≤ 0.2 V, and at rather high, V ≥ 2 V, forward voltages. The characteristic times of these relaxation processes ranged from ~1 µs to 10³s. The exponential part of the current-voltage characteristic was only weakly affected by irradiation. The temperature dependence of the base resistance changed expo-nentially with temperature with activation energy E_a ~ 0.6 eV, indicating that the Z_1/2 level plays a dominant role in this process. The temperature increase also led to the increase of the ideality factor from 1.05 at 25 °C to 1.1 at 172 °C. At elevated temperatures and high forward voltages V > 2-4 V, the current voltage characteristics tend to be super-linear. It is concluded that at high voltages, the space charge limited current of majority carriers (electrons) and hole injection from the p-n regions play an important role in the formation of the current voltage characteristic. The frequency dependences of noise spectral density S of proton irradiated Schottky diodes have the unusual form of S ~ 1/f⁰⁵. [ABSTRACT FROM AUTHOR]