Formation of Eu3+ Luminescent Centers in Eu-Doped ZnO Grown by Sputtering-Assisted Metalorganic Chemical Vapor Deposition

The photoluminescence (PL) and electrical properties of Eu-doped ZnO (ZnO:Eu) grown by sputtering-assisted metalorganic chemical vapor deposition (SA-MOCVD) were investigated. Sharp PL lines due to intra-4f transition in Eu3+ ions were observed when ZnO:Eu was annealed at temperatures (T a) higher than 500 °C in O2 ambient. In Hall measurements, the as-grown ZnO:Eu showed a high electron density of 3×1019 cm-3, indicating that the doped Eu ions act as a donor in ZnO. The electron density decreased rapidly at T a≥500 °C and was 2×1017 cm-3 at T a = 600 °C. These results revealed that a complex consisting of a Eu3+ ion and an interstitial oxygen (Eu3+–Oi complex) is formed by high-temperature annealing and acts as a Eu3+ luminescent center in ZnO.