缺陷对氧化锌激子发光效率的影响机制

Due to its excellent properties such as very high exciton binding energy which allows highly efficient excitonic luminescence and low-threshold lasing, ZnO, a wide bandgap semiconductor, is regarded as a promising material for thin-film and nanoscale light-emitting devices. However, the internal quantum efficiency of excitonic emission is rather low in practical ZnO materials because of the dominant nonradiative recombination and defect-related emissions, with the mechanisms still unclear. Aiming at the key issues of the rarely-studied nonradiative defect centers and the controversial origin of the 3.31 eV emission (A line), in this project we are dedicated to investigate the influences and mechanisms of defects on the room temperature excitonic luminescence efficiency of MBE-grown ZnO films and MOCVD-grown ZnO nanostructures via identification and control of the point and extented defects, such as zinc vacancy and stacking faults. We expect to identify the atomic nature of the nonradiative defect centers, to clarify the contribution of stacking faults to the A line emission, and to reveal the recombination dynamics of excitons on the defects.Accordingly, we expect to enhance the internal quantum efficeincy of the room temperature excitonic emission in ZnO films and one-dimensional nanostructures via controlling the growth parameters. It is believed that the studies of this project will enrich the fundamental physics of ZnO luminescence. It has great scientific significance and potential applications in future optoelectronic devices.

宽带隙半导体ZnO具有激子束缚能高等优点，可望获得高效激子发光和低阈值激射，在薄膜和纳米发光器件方面均有广阔的应用前景。但由于缺陷发光和非辐射复合中心的影响，实际ZnO材料激子的室温发光内量子效率不高，其影响机理还有待深入研究。本项目拟以分子束外延(MBE)和金属有机化学气相沉积(MOCVD)等方法生长的高质量ZnO薄膜和纳米结构为研究对象，针对ZnO中非辐射复合中心指认以及3.31eV(A线)发光起源这两个关键科学问题，通过对锌空位等点缺陷以及层错等扩展缺陷的识别和控制，深入研究缺陷对ZnO室温激子发光效率的影响规律，指认缺陷非辐射复合中心，阐明层错缺陷对A线发光的影响机制，揭示激子在缺陷处的复合动力学过程。在此基础上，优化生长工艺，制备低缺陷密度ZnO薄膜和纳米结构，提高室温激子发光的内量子效率。本项目研究将丰富ZnO发光的知识体系，具有重要的科学意义和潜在应用价值。

宽带隙半导体ZnO具有激子束缚能高等优点，可望获得高效激子发光和低阈值激射，在发光器件方面具有广阔的应用前景。但由于缺陷发光和非辐射复合中心的影响，实际ZnO材料激子的室温发光内量子效率不高，因此必须深入研究其影响机理。本项目以高质量ZnO单晶、薄膜和一维纳米结构为研究对象，针对ZnO中3.31eV(A线)发光起源和非辐射复合中心指认这两个关键科学问题，通过对锌空位等点缺陷的识别和控制，深入研究了缺陷对ZnO室温激子发光效率的影响规律，取得了如下主要结果：1）确定了A线发光的物理起源是自由激子一级声子伴线和自由电子到层错的跃迁这两种机制的竞争，且这种竞争关系强烈依赖于温度；2）发现和指认了InZn-VZn复合体等若干种点缺陷，阐明了这些点缺陷的电子态和光跃迁机制，推断锌空位相关缺陷是一种非辐射复合中心；3）系统研究了ZnO中激子的复合动力学过程，揭示了激子局域、激子-声子耦合等辐射与非辐射复合通道；运用掺杂、离子注入等方法，调控杂质和缺陷密度，探索了提高ZnO激子发光内量子效率的途径，将室温内量子效率最高提高到40%以上。本项目研究丰富了ZnO发光和缺陷物理的知识体系，为ZnO基发光器件的性能提升提供了科学依据和可能途径，具有重要的科学意义和潜在应用价值。