Abstract
The focus of this thesis is on the study of the surface morphology and optical properties of nitride-based materials grown by radio frequency plasma assisted molecular beam epitaxy, including the growth and analysis of GaN thin films and nanorods. Firstly, Chapter 1 is the motivation of this study and the review introduction of nitride-based materials. The operation principles and mechanisms of epitaxy system and relative measurement equipments adopted in this study are introduced in Chap 2. These equipments include plasma assisted molecular beam epitaxy system, reflection high energy electron diffraction system, scanning electron microscopy, transmission electron microscopy, micro-photoluminescence spectroscopy and micro-Raman scattering spectroscopy. In Chapter 3, the surface polarities of GaN thin films grown on different buffer layers are discussed in this chapter. With different buffer layers grown on [0001] plane sapphire substrates under different temperatures, GaN thin films are grown on them. The different buffer layers include low-temperature GaN and high-temperature AlN. Ga polarity is observed on the GaN thin film grown on high-temperature AlN buffer, while N polarity is observed for low-temperature GaN buffer. In Chapter 4, GaN nanorods grown on Si(111) substrates are investigated. The influence of different growth parameters like substrate temperature and V/III ratios are investigated in this chapter. The surface and optical properties of the samples are also investigated in this chapter. Chap 5 is the conclusion.