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

Abstract

The current voltage characteristics and the low-frequency noise in high voltage 4H-SiC junction barrier Schottky diodes irradiated with high energy (15 MeV) protons were studied at different temperatures and irradiation doses Φ from 3 × 1012 cm−2 to 1 × 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 103 s. The exponential part of the current-voltage characteristic was only weakly affected by irradiation. The temperature dependence of the base resistance changed exponentially with temperature with activation energy Ea ∼ 0.6 eV, indicating that the Z1/2 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/f 0.5.