Synthesis And Characterization Of GaAs Material

GaAs is one of the most important Ⅲ-Ⅴ direct band gap (Eg=1.424eV) compound semiconductor materials, owing to its high electron mobility and excellent photoelectric properties, it has been widely used in the manufacture of microwave devices, infrared photovoltaic device and solar cells. As a very important optoelectronic and microelectronic materials, GaAs has attracted a significant attention, and become a focus in the field of semiconductor science.Many crystal growth methods, such as Hot Wall Epitaxy Method, Molecular Beam Epitaxy, and Metal Organic Chemical Vapor Deposition, were used in the production of GaAs materials in industrial. However, the complex equipment and high cost were unfavorable, so how to use a simple way for preparation of GaAs materials became a focus of research. In this paper, the synthesis and growth mechanism of GaAs nano-scale thin films were investigated by a two-step electrodeposition method. And, the GaAs octahedrons powder and GaAs films were obtained by the hydrothermal method, the crystal structure, morphology, optical properties and growth mechanism were also investigated systematically. The main results were as follows:1. GaAs nano-scale films were successfully prepared on the FTO glass substrate by a two-step electrodeposition method with appropriate annealing process. The GaAs films synthesized at different annealing temperatures were characterized by XRD, FESEM, UV-Vis and PL. It had been found that the optimum annealing parameters of preparation of GaAs films was300℃for2hours. The GaAs films obtained under this condition were face-centered cubic structure, the particle size was even, the ratio of Ga and As was close to1:1, and PL spectra showed red fluorescen phenomenon. With the increase of annealing temperature, the amount of particles also increased, the ratio of Ga and As changed, the band gap decreased, The formation mechanism of the GaAs films was also discussed.2. GaAs octahedrons were synthesized via a simple hydrothermal method using Ga and As2O3as reactants. It had been found that the crystalline phase and morphology of the products were dependent on the reaction conditions, such as the molar ratio of Ga and As2O3, the concentration of HC1, the reaction time and the annealing temperature. Changing the reactant mole ratio might lead to produce impurities, lower acidity (<2mol/L HC1) would result in the incompleteness of reaction, on the contrary, higher acidity (>2mol/L HC1) would promote the hydrolysis of GaAs products, and destroy the morphology of the octahedron. With the increase of annealing temperature, GaAs octahedral size increased gradually, crystallinity was improved. With the extension of reaction time, the GaAs product experienced the transformation from nanoparticles to octahedral structure. The optimum parameters of the GaAs octahedrons obtained by hydrothermal method were as follows:2:1molar ratio of Ga and As2O3,2mol/L HC1, reaction at190℃for20h, annealing at300℃for1h. XRD and FESEM results showed the GaAs octahedron was homogeneous and smooth without any impurities. And the formation mechanism of GaAs octahedron was also discussed. 3. GaAs films were successfully obtained on the Ti substrate by a simple hydrothermal method. The film was face centered cubic structure, and composed of spherical particles, while the effect of reaction time on the film was investigated, the appropriate reaction time was15hours. The emission peak was at879nm infrared emission.