Effects of high dose proton irradiation on the electrical performance of ZnO Schottky diodes

Bulk ZnO Schottky rectifiers with Pt rectifying contacts were exposed to 40 MeV protons at fluences from 5 × 10⁹ to 5 × 10 ¹⁰ cm^-2. These doses correspond to that received in more than 10 or 100 years, respectively, in low earth satellite orbit. The reverse breakdown voltage of the ZnO diodes increased from ∼3.2 V (taken at a current density of 0.1 A/cm²) in unirradiated devices to ∼3.9 V after the highest proton dose. The effective barrier height decreased with proton dose from 0.37 eV to 0.35 eV while the diode ideality factor increased from 1.8 to 1.9 for the 5 × 10¹⁰ dose. The very high tolerance of the ZnO diodes to high doses of energetic protons suggests that this material is well-suited to applications requiring high radiation tolerance.