Gan - Based Heterostructure Strain Analysis And Electrical Properties Of Materials

As an important III-V group's nitride, GaN recently had been a central issue of the research and used widely in the area of photo-detectors, high temperature and high power devices, and the evil condition. But a high strain or stress existed in the GaN epitaxy because of the large mismatch of the lattice constant and the thermal coefficient, which had an effect on the photo and electrical properties. In this article, the residual strain, electrical property and the relationship of them had been researched.In the introduction of this master thesis, the potential applications of the GaN thin films and preparation methods et al had been reviewed. On the basis of the review, the investigation of the structure-properties of GaN thin films by X-ray diffraction methods was proposed. Main content of the thesis were also given in the introduction. The thesis focused on using different measure methods of HRXRD (High Resolution X-ray diffraction), Hall test and AFM to study the residual strain and electrical properties of the GaN thin films detailly.1. The HRXRD, Hall test and AFM test had been used to figure the residual strain, crystal quality and the electrical property of the GaN grown on the sapphire with a buffer layer HT-AlN or LT-GaN, and of the Mg doped GaN. The result had revealed that the strain could be relaxed in the form of the formation of the disorder, mis-orientation of the lattice and the ups and downs of the surface. But the periodicity of the lattice could be deteriorated by the disorder induced by the strain relaxation, and then reduced the carrier mobility.2. The Si-doped and annealed GaN film had been researched, as well as the damage of the crystal lattice, the electrical properties and the relationship of them especially. These results had shown that the Si implantation induced the lattice damage, which would be deteriorated with the increase of the Si dose. The crystal lattice damage, the main scattering centre of the carrier had been partly repaired by annealing. Simultaneously, the higher electrical active efficiency and carrier mobility could be achieved with the improvement of the annealing-temperature. 3. The film strain and the RSM (Reciprocal Space Map) strain gradient of the AlGaN/AlN super-lattice had been researched by the HRXRD and AFM et al, as well as the Al-component and the parameter of the super-lattice. These researches had revealled that the strain could be regulated, and the disorder could be filtered by the structure of the super-lattice, and the film quality could be improved with the increase of the number of the period of the AlGaN/AlN super-lattice.