Irradiation Effect of 8MeV Protons on Single-Crystalline Zinc Oxide Films

Wide-bandgap semiconductor ZnO potentially exhibits high radiation hardness since large displacement threshold energy of constituent atoms can be expected due to the small lattice constant and large bandgap energy. To study the radiation hardness, the effect of proton irradiation on single-crystalline n-type ZnO films was examined. These films were grown by molecular beam epitaxy, and irradiated by 8MeV protons with fluences of 1.4 × 10 15 , 2.8 × 10 15 , 5.6 × 10 15 and 1.4 × 10 16 p/cm 2 . A rapid increase of electrical resistance by a decrease of carrier density was observed with a threshold fluence of about 1 × 10 15 p/cm 2 . This change in electrical properties was associated with a steep deterioration of the near-bandedge emission intensity in cathodoluminescence. These radiation damages were found to recover after a thermal annealing over 600°C. Such high radiation hardness of ZnO exceeds that of GaN, indicating promising application of this material to space- and nuclear-electronics.