Microscopic Luminescence Properties of ZnO and ZnO Based Heterostructures

The optical properties of excitonic recombinations in ZnO are investigated by spatially and spectrally resolved cathodoluminescence measurements. The relevance of cathodoluminescence microscopy as a spatially resolved luminescence technique as a simple but very powerful characterization method is stressed out in discussions of a wide variety of appropriate examples. A thorough discussion of the various features of the cathodoluminescence of an undoped ZnO bulk crystal, epitaxially grown ZnO and MgZnO/ZnO/MgZnO quantum well structure is given. Particular attention is devoted to the impact of the internal electrical fields, e.g. the Franz-Keldysh effect in ZnO. Furthermore, this study focuses on the spectral variations as a function of depth to the interface in ZnO homo- and heterostructures. Our aim is to establish the nature of the optical transitions influenced by internal fields, defects and impurity doping in ZnO/GaN and ZnO/ZnO interfaces. This review covers also the vertical transport, diffusion and capture of carriers in a MgZnO/ZnO/MgZnO quantum well structure.