Synthesis And Characterization Of GaN Films And Nanorods

In recent years, Gallium Nitride as a wide band gap semiconductor has attracted more and more attention mainly due to its promising applications in short-wave light-emitting devices, photodetectors, as well as anti-radiation, high frequency and high power electronic devices. The growth of high quality GaN crystal is the premise for the development of GaN-based devices. At present, Most of GaN-based devices are fabricated on sapphire. However, served as substrate sapphire has many disadvantages to the device fabrication processes, such as insulating nature, hard to cleave. Silicon, as the most important semiconductor material, should be another promising substrate for GaN because of its available in larger size, lower cost and conductive. Therefore, the investigation of GaN epitaxy on silicon is of extreme practical importance.In this thesis, we first presented a comprehensive review of the research history and current status of GaN material preparation and GaN-based devices processing. On the basis of our MOCVD system, we conducted a detailed study of GaN epitaxy on silicon substrate, and we also studied mechanism of GaN nanotube growth. The obtained results are as the following:(1) Using low-temperature and high temperature AlN as the buffer layers respectively, we studied the quality of GaN films related to the buffer layer's growth temperature, thickness, V/III and the composition of carrier gas. We obtained high-quality GaN films crackless using 170nm high-temperature AlN as the buffer layer.(2) We synthesized the GaN nanorodes at 900 ℃, using Ni as the catalyst. The obtained nanorods were charatcterized by X-ray diffraction, field emitting scanning electron microscope, transmission electron microscope, and X-ray energy dispersive spectrometer. The results showed that the nanorods crystallized as pure hexagonal GaN phase, and grows along the [0001] direction. We also discussed the possible formation mechanism of the final needle shape nanorodes.