ZnO纳米结构中激子和光学声子的耦合调控及其发光特性

Exciton and optical-phonon interaction is an important physical process in semiconductor luminescence that significantly affects the spectral features of the band-edge emission. As a typical direct and wide bandgap semiconductor, ZnO luminescence is susceptible to the exciton and optical-phonon interaction. In recent years various factors have been found to be closely related to the ZnO exciton and optical-phonon interaction, such as defect/impurity, surface roughness, size, crystal face, and etc. However, controversies about the physical mechanism still exist. In addition, the phenomenon of energy shift in the exciton’s first phonon relica, as well as its origin (i.e., LO or TO), so far have not been well understood. This project is to study the various physical processes and mechanisms that affect the ZnO exciton and optical-phonon interaction, which will be conducted by systematical controlling the intrinsic physical properties and external surrounding environments of the ZnO nanostructures, through measuring the spatially- and angularly-resolved variable- temperature photoluminescence and cathodoluminescence. We hope to quantify the energy shift and spectral contribution of the exciton’s first phonon relica and identify its origin, and to achieve the capability to manipulate this interaction. This project is helpful for a further and better understanding of the ZnO exciton luminescence, which also can be very useful for the design of ZnO-based photonic devices by providing the necessary physics and more designing ideas.

激子与光学声子的相互作用是半导体发光中的一个重要物理过程，对半导体室温带边发光的峰形和峰位都有显著的影响。氧化锌是一种典型的容易受到该过程影响的直接宽带隙半导体，近年来人们已发现与氧化锌激子与光学声子相互作用强度关联的众多因素，包括缺陷/杂质、表面粗糙度、纳米结构的尺寸和晶面等，但是对相关机理的研究仍然存在较大争议。除此之外，诸如氧化锌激子第一声子伴线的峰位移动现象、其来源究竟是LO还是TO声子的问题，目前还没有被很好的理解。本项目拟通过调节氧化锌纳米结构的内禀物理参量和外在环境参量，利用空间分辨和角分辨光致荧光和阴极射线荧光测量技术，较为系统地研究若干种影响氧化锌激子与光学声子相互作用的物理过程及其机理，探究激子第一声子伴线峰的来源和峰位移动的原因，最终实现对该相互作用的有效调控。该项目有利于提高人们对氧化锌激子发光相关物理过程的认识，也可为设计氧化锌基光子器件提供物理基础和设计思路。

本项目以氧化锌激子与声子相互作用为研究对象，在其物理机理和光谱探测技术上取得了一定的进展。一方面我们纠正了常规的激子与声子相互作用判定方法，另一方面确定了第一声子伴线是来自于LO声子而不是TO声子。同时我们搭建了集成空间分辨和角度分辨一体化的光学测量系统，发展了边界散射的光学测量方法。