Collaborative Research: Studies of Electron Injection-Induced Effects in ZnO-based Materials and Device Structures

随着ZnO外延生长和加工的最新进展，在不久的将来很有可能实现高效的少数载流子器件，如发光二极管、激光二极管和透明p-n结。由于zno基半导体的少数载流子扩散长度（决定pn结性能的关键参数之一）通常小于1微米，因此寻找改进方法势在必行。主要研究人员最近的发现表明，由于电子注入，p型ZnO中的少数载流子扩散长度可以延长。虽然观察到的新效应归因于杂质相关水平的电子捕获，但延伸缺陷和点缺陷以及表面状态的作用并不能完全排除。本研究的智力价值在于探索电子注入对ZnO及其相关化合物中少数载流子输运和重组的影响。广泛的外延掺锑p型ZnO和p型Zn1-xMgxO (x ？将研究t0.15)层。此外，p-ZnO掺杂其他杂质如磷或氮，以及p型Zn1-xCdxO (x ？t0.15)和Zn(Mg/Cd)O/ZnO超晶格，将进行研究。镁（镉）掺入ZnO晶格和势垒以及在超晶格中的良好存在产生了不同于ZnO中的电子注入条件。为了充分了解Zn(Mg/Cd)O中电子注入的影响，并找到它们可以被使用的条件，系统的电学和光学研究将在具有代表性的器件结构范围内进行：p-n结和肖特基二极管。电气测试，结合电子束感应电流测量，将在扫描电子显微镜下进行。这些测量将辅以原位阴极发光以及光谱光响应和瞬态光电流测量。所研究的电子注入效应可能与掺杂剂浓度、外延层质量和组成有关。因此，有必要研究具有这些特性变化的材料。这些材料的生长及其器件结构的制造和表征是通过中佛罗里达大学和加州大学河滨分校的团队之间的互动合作来保证的。本研究的实际意义在于光电探测器等pn结电荷收集半导体器件的性能控制，其中少数载流子扩散长度起着至关重要的作用。光电探测器的量子效率预计将比目前的15-20%提高几倍。这个合作项目的更广泛的影响是更好地了解zno基半导体的点和扩展缺陷的基本原理，在两所大学之间建立伙伴关系，并整合研究生，本科生和K-12级别的研究和教育，正如在拟议研究中代表不足的博士生，一些本科生和当地高中生的参与所表达的那样。这些学生将在参与拟议的研究时，建立长期、远程学术项目合作的技能。

ECCS 0900971/0900978Collaborative Research: Studies of Electron Injection-Induced Effects in ZnO-based Materials and Device Structures With recent advances in ZnO epitaxial growth and processing, it is very likely that efficient minority carrier devices, such as light emitting diodes, laser diodes and transparent p-n junctions, can be achieved in the near future. Because the minority carrier diffusion length - one of the critical parameters in defining p-n junction performance - is usually less than 1 micron in ZnO-based semiconductors, it is imperative to find ways of its improvement. The principal investigators¡¦ recent findings indicate that the minority carrier diffusion length can be elongated in p-type ZnO due to electron injection. While the observed novel effect was attributed to electron trapping on impurity-related levels, the role of extended and point defects as well as of surface states was not completely excluded. The intellectual merit of this research is in exploration of electron injection¡¦s impact on minority carrier transport and recombination in ZnO and related compounds. A wide range of epitaxial antimony-doped p-type ZnO and p-type Zn1-xMgxO (x ?T 0.15) layers will be studied. In addition, the minority carrier transport in p-ZnO doped with other impurities such as phosphorus, or nitrogen, as well as in p-type Zn1-xCdxO (x ?T 0.15) and Zn(Mg/Cd)O/ZnO superlattices, will be investigated. Magnesium (Cadmium) incorporation into the ZnO lattice and barrier and well presence in the superlattices create electron injection conditions different from that in ZnO. To fully understand the effects of electron injection in Zn(Mg/Cd)O and to find conditions under which they can be employed, systematic electrical and optical studies will be carried out in the representative range of device structures: p-n junction and Schottky diodes. Electrical testing, combined with Electron Beam-Induced Current measurements, will be performed in-situ in a Scanning Electron Microscope. These measurements will be complemented with in-situ cathodoluminescence as well as spectral photoresponse and transient photocurrent measurements.The effects of electron injection to be investigated are likely related to concentration of dopants, epitaxial layer quality and composition. Therefore, the study of materials with variations in these properties is necessary. The growth of these materials and the fabrication and characterization of their device structures are assured through the interactive collaboration between the groups at the University of Central Florida and the University of California, Riverside. The practical significance of the proposed research is in performance control of p-n junction charge collection semiconductor devices, such as photodetectors, in which the minority carrier diffusion length plays a critical role. A several-fold increase in the photodetector¡¦s quantum efficiency is anticipated relative to the current state-of-the-art of ~ 15-20%. The broader impact of this collaborative project is in better understanding the fundamentals of point and extended defects in ZnO-based semiconductors, creating a partnership between two universities, and integrating research and education at the graduate, undergraduate and K-12 levels, as expressed in participation of underrepresented Ph.D. students, several undergraduates and local high school students in the proposed research. These students will build skills in collaborating on a long-term, long-distance academic project, as they participate in the proposed research.