Proton irradiation of ZnO Schottky diodes

Zinc oxide is generally considered to be radiation hard, although there are few experimental reports supporting this assertion. In this paper, we present results on the changes in electrical performance of bulk Pt/ZnO Schottky rectifiers exposed to 40-MeV protons at fluences from 5 X 10(9) cm(-2) to 5 X 10(10) cm(-2). These doses correspond to more than 10 years or 100 years, respectively, in low-earth satellite orbit. The reverse breakdown voltage of the ZnO diodes increased from similar to 3.6 V in unirradiated devices to similar to 4 V after the highest proton dose. The effective barrier height decreased with proton dose, while the diode ideality factor increased from 1.8 to 1.9 for the highest dose. These devices appear promising for both aerospace and terrestrial applications where irradiation hardness is a prerequisite. The main degradation mechanism appears to be creation of recombination centers and traps.