Group-V impurities induced native point defects and related visible luminescence in pulsed-laser-deposited ZnO thin films
摘要
Native point defects play a major role in controlling optical and electrical properties of ZnO material. We report several visible emission bands associated with native point defects in pulsed-laser-deposited ZnO, P: ZnO and P, N: ZnO thin films. P- and N-codoped ZnO exhibited characteristic Raman modes at 276 cm−1 and 582 cm−1 related to nitrogen-induced zinc interstitials and oxygen vacancies, respectively. Integrated PL intensity of the visible emission increases for doped ZnO films relative to undoped ZnO. Photoluminescence (PL) and photoluminescence excitation (PLE) measurements reveal that violet and blue emissions are result of the electronic transitions from conduction band to zinc vacancies and from zinc interstitials to valence band, respectively. However, green and orange-red emissions are attributed to the transitions from energy levels involving oxygen vacancies and interstitials to valence band respectively. The emission band at 464 nm is attributed to the transition from zinc interstitials to zinc vacancies. An energy-level diagram indicating the transitions associated with various native points defects is proposed.