Synthesis, Doping And Luminescence Properties Of GaN Nanometer Materials

Semiconductor nanomaterials have been the research hotspot in the nanomaterial science, not only because of their unique properties but also because of their potential application value in the development of device miniaturization. Ga N nanomaterials as an important kind of wide bandgap semiconductor materials, their study of controllable preparation, optical properties and the deep level behavior of band structure has always been the research hotspot. Concurrently, recent studies have found that Ga N-based nanomaterials possess the property of absorption of visible light which makes the hydrolysis to generation hydrogen, as a consequence different morphology of Ga N nanomaterials in the study of preparation and optical properties obtained wide attention again.In this thesis, by solid-phase source chemical vapor transport method, a variety of Ga N nanostructures were prepared without catalyst on the quartz substrate, through the direct reaction of metal Ga and ammonia. The structure, morphology and optical property of the synthesized samples were characterized by XRD, SEM, Raman and PL spectra. The results of the study are as follows:1. Within 0.1 atmospheres of pressure, Ga N nanostructures were prepared without catalyst on the quartz substrate. Nanostructures are stacked by the nanocrystalline along their appropriate direction.The synthesis of nanostructures with morphological diversity can be attributed to different growth temperature which will lead to different metal Ga vapor pressure concentration. In Raman spectra of Ga N nanostructures, compared with bulk phase, A1(LO) model produced a red shift, which can be attributed to the phonon confined effect. Photoluminescence of Ga N nanostructures include band-edge luminescence and defect luminescence. The defect luminescence can be attributed to radiation recombination from shallow donor level to valence band or from shallow donor level to deep acceptor level.2. Under atmospheric pressure, Ga N nanostructures were prepared near the gallium source and on the quartz substrate without catalyst. By changing heating method, temperature, ammonia flow rate, reaction time and other means to control the morphology of wurtzite Ga N nanostructures. With the increase of reaction temperature, grain size becomes bigger. As synthesis temperature reaches 900℃, the crystal quality becomes better. As reaction time becomes longer, crystal quality also becomes better. Compared with Ga N nanostructures which were synthesized under negative pressure, nanostructures which were synthesized under atmospheric pressure own better crystal quality. With the decrease of grain size, photoluminescence of defects will produce redshift, which can be attributed to a certain range of deep acceptor level.3. Zn-doped Ga N nanostructures can form coating structure, the size of nanostructures increases, samples become thick, which shows that Zn doping can improve the vapor pressure of Ga. XRD patterns will produce small shift to the left, lattice constants increase slightly, diffraction peaks become more obvious, which show Zn doping can improve the crystallinity of Ga N nanostructures.