Abstract O-polar and Zn-polar ZnO films were grown on c-sapphire by pulsed laser deposition. Positron annihilation spectroscopy study reveals that the VZn-related defects in the ZnO films with different polarities are different in structure and their thermal evolution is different. Hall effect measurement and luminescence spectroscopy reveal that the electrical and optical properties and their corresponding thermal evolution are strongly dependent on the polarity of the film. The luminescence spectra of the as-grown Zn-polar ZnO film is signified by a negligible green defect emission (at ~ 2.4 eV) and strong near band edge emission as compared with the O-polar film. The as-grown Zn-polar film exhibited a lower electron concentration (2 × 1018 cm−3) than that of the O-polar film (6 × 1018 cm−3); this difference is attributed to their different H concentrations. For the O-polar film, the electron concentration decreased with annealing temperature Tanneal, reaching a minimum at 700°C and then increased to 4 × 1018 cm−3 at Tanneal = 900 °C. In comparison, the electron concentration of the Zn-polar ZnO film monotonically decreased with Tanneal attaining a value of ~1 × 1017 cm−3 at Tanneal = 900 °C, 40 times smaller than that of the O-polar film. The cause for the differences in the optical and electrical properties for the O-polar and Zn-polar films is explained by the presence of different defects in these films.

中文翻译：

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通过脉冲激光沉积生长的 O 极性和 Zn 极性 ZnO 薄膜的电学和光学特性

摘要 通过脉冲激光沉积在 c-蓝宝石上生长 O 极性和 Zn 极性 ZnO 薄膜。正电子湮没光谱研究表明，不同极性的ZnO薄膜中VZn相关缺陷结构不同，热演化也不同。霍尔效应测量和发光光谱表明，电学和光学特性及其相应的热演化强烈依赖于薄膜的极性。与 O 极性薄膜相比，生长的 Zn 极性 ZnO 薄膜的发光光谱由可忽略不计的绿色缺陷发射（~2.4 eV）和强近带边缘发射表示。生长的 Zn 极性薄膜表现出比 O 极性薄膜 (6 × 1018 cm−3) 低的电子浓度 (2 × 1018 cm−3)；这种差异归因于它们不同的 H 浓度。对于 O 极性薄膜，电子浓度随退火温度 Tanneal 降低，在 700°C 时达到最小值，然后在 Tanneal = 900 °C 时增加到 4 × 1018 cm-3。相比之下，Zn 极性 ZnO 膜的电子浓度随着 Tanneal 在 Tanneal = 900 °C 下达到 ~1 × 1017 cm-3 的值而单调降低，比 O 极性膜小 40 倍。O 极性和 Zn 极性薄膜的光学和电学性能差异的原因可以通过这些薄膜中存在的不同缺陷来解释。Zn 极性 ZnO 薄膜的电子浓度随着 Tanneal 在 Tanneal = 900 °C 下达到 ~1 × 1017 cm-3 的值而单调降低，比 O 极性薄膜小 40 倍。O 极性和 Zn 极性薄膜的光学和电学性能差异的原因可以通过这些薄膜中存在的不同缺陷来解释。Zn 极性 ZnO 薄膜的电子浓度随着 Tanneal 在 Tanneal = 900 °C 下达到 ~1 × 1017 cm-3 的值而单调降低，比 O 极性薄膜小 40 倍。O 极性和 Zn 极性薄膜的光学和电学性能差异的原因可以通过这些薄膜中存在的不同缺陷来解释。