Reduction of defect states of tantalum oxide thin films with additive elements

Electrical properties of tantalum oxide (Ta₂O₅) thin films formed by metalorganic decomposition have been studied with respect to their defect states. A shallow band of defect states, which are the origin of hole traps, is detected by thermally stimulated current. The defect states in the Ta₂O₅ films are fully suppressed with additive elements such as TiO₂ and WO₃. It is considered that oxygen vacancies are fully compensated by Ti⁴⁺ ions or W⁶⁺ ions that are substitutionally incorporated into Ta⁵⁺ sites.