The effects of high-energy proton irradiation on the electrical characteristics of Au/Ni/4H-SiC Schottky barrier diodes

Au/Ni (20:80) Schottky barrier diodes (SBDs) were resistively evaporated on nitrogen-doped n-type 4H-SiC. Current-voltage (I-V) and capacitance-voltage (C-V) characteristics of the SDBs were investigated before and after bombardment with 1.8 MeV proton irradiation at a fluence of 2.0 × 1012 cm-2. The measurements were carried out in the temperature range 40-300 K in steps of 20 K. Results obtained at room temperature (300 K) showed highly rectifying devices before and after bombardment. It was observed that the proton irradiation induced an increase of ideality factor from 1.05 to 1.13, a decrease in Schottky barrier height from 1.40 to 1.22 eV, an increase in series resistance from 10 to 66 Ω and a noticeable increase of the saturation current from 3.0 × 10-21 to 6.8 × 10-17 A. The increase in saturation current after proton irradiation was attributed to the presence of interfacial states created by irradiation-induced defects. Thermionic emission dominated the I-V characteristics in the temperature range 120-300 K but the I-V characteristics deviated from thermionic emission theory at temperatures below 120 K for devices both before and after irradiation. The variation of the SBDs characteristics with temperature was attributed to the presence of lateral inhomogeneities of the SBH. Modified Richardson constants were determined from a Gaussian distribution of barrier heights to be 133 and 165 A cm-2 K-2 before and after irradiation, respectively.