Study On Preparation And Application Of GaN/AlN Core-shell Nanowires

The fast development of IT industry promotes microelectronic technology changing quickly.Semiconductor materials fabricated as one-dimensional offer a series of fascinating physical properties different from bulk materials and has been a focus of attention.With further research,one-dimensional heterogeneous nanostructure,possessing the advantages of both materials,were design to realized various functions materials.The core-shell nanowires is an ideal material for study,showing multi-functionalized characteristics(such as optical,electrical,magnetic,and thermal properties),which is superior to single materials,and may the research trends in the field of composite materials.GaN and AIN,as the representative of the nitrogen compounds in the genus,are the basic materials for developing luminescent lighting and detecting laser devices.The combination of the two materials provides a wide space for the application of nanomaterials,and has great potential in the field of optoelectronics,microelectronics and new energy.Therefore,this paper studies the theoretical and experimental research on the GaN/AIN core-shell nanowires.The electronic structures and optical properties of GaN/AIN core-shell nanowires in different core-shell ratio and sizes have been investigated on the base of DFT,suggesting that GaN/AIN core-shell nanowires has the rationality for its existence and exhibits a fairly good stability as the hexagonal wurtzite structure.Different characteristic peaks appear at the valence band maximum,which caused by the hybridization between Al p-states and N p-states.And the energy band gap is broadened as the conduction band shift toward higher energy region.Also,the band gap declines with increase of GaN core diameter,while being almost invariably when increasing the cycles of shell AIN.Optical characteristics testifies the anisotropy of the crystal.The intensity of imaginary part of dielectric function goes on increasing,which increases the electron transition capacity of the GaN nanowires.And the real part of dielectric function also moved to the high energy region,the band gap changes correspondingly,which may regulate the optical properties of core shell ratio.The material appears transparency in the visible range,then absorption bandwidth narrowed,reason for the whole spectrum showing a blue shift enters to UV region is due to the band broadening.So that it might be a shielding material material for ultra-violet radiation.Then the thesis establishes a method of preparing GaN/AlN coe-shell nanowires on Si substrates based on chemical vapor deposition in two steps,discussing the following contents:Effect of growth parameters on samples,the growth mechanism of core-shell structures,and the optimal parameters were obtained.Final products were characterized and the results show GaN/AlN core-shell nanowires were hexagonal wurtzite with strong c-axis preferred orientation,and presents a high degree of crystallinity.The blue shift in PL spectrum proves that this core-shell structure may regulate the optical properties,and has a promising future in ultra-violet field.