Fabrication and characterization of a Pt/MgxZn1−xO/ZnO Schottky barrier photodiode utilizing a field plate structure

We fabricated a Pt/MgxZn1−xO/ZnO Schottky barrier photodiode (SBPD) utilizing a field plate structure and investigated the characteristics of its electric property toward realization of a high-gain avalanche photodiode for feeble ultraviolet ray detection. A MgxZn1−xO film on the Zn-face of a c-ZnO substrate was grown by the plasma-assisted MBE method. The fabricated Pt/MgxZn1−xO/ZnO SBPD showed a low reverse current and a high breakdown voltage of −380 V, and several SBPDs showed high breakdown voltage in excess of the measurement limitation of −500 V. The high breakdown voltage was achieved by a low density of defects in both the MgxZn1−xO film and ZnO substrate and the field plate structure, and therefore a depletion layer reached the bulk of the ZnO substrate through the MgxZn1−xO film.