Synthesis And Growth Mechanism Of GaN And Ga₂O₃Nanomaterials

With the development of Semiconductor Optoelectronic Technology, the study of wide-band-gap semiconductor material has become hot off the press. GaN and Ga2O3are both favorable wide-band-gap semiconductor materials. GaN which is a typical representative of the third generation semiconductor material, is one of the most promising materials for fabrication of blue-emitting diodes and high-power optoelectronic devices. Being a kind of Metallic Organic Semiconductor materials, Ga2O3will have good potential applications to gas sensors, ultraviolet detectors, deep ultraviolet transparency electrodes and solar cells. The properties of the low-dimensional materials only can be well studied under the conditions of large-scale synthesis, cleanliness, and size, microstructure and component controllable. The nano devices can be packaged next. However, the study of GaN and Ga2O3nanomaterials synthesized on Si substrates, microstructures, growth mechanisms and their physical properties is still in its infancy at present. Still there are a number of buring problems. Thus, it is necessary for us to do an in-depth study in these aspects.Monocrystalline silicon was employed to be used as substrates in this work. The repeated siftings have brought reasonable raw materials, synthesis methods and process parameters. GaN and Ga2O3low-dimension materials can be synthesized on the Si substrates. Analytical reagent Ga2O3powder was selected as gallium source in this work. GaN and Ga2O3nanostructures with different morphologies were synthesized on the substrate of Si by chemical vapor deposition, and the synthesis process was improved on the basis of the previous research work. The growth mechanism of these nanostructures was also discussed. The conclusions can be drawn as follows:(1) The morphology of the as-synthesized products can be affected by the admission proportions of two sorts of gases, NH3and Ar, and the placement location of the Si substrates at the temperature of950℃without using catalysts. The1:1ratio of the flow rates of NH3and Ar, and the location of Si substrate is15cm from the source are two optimal parameters for synthesizing of high-quality GaN nanowires. The growth mechanism of GaN nanowire is a kind of synergistic reaction of Ga, produced by Ga2O3analysis, self-catalysis and developing self-catalysis according to the VLS growth mechanism.(2) GaN film can be deposited on the Si substrates which located in the range of 12-17cm from the center of the furnace as the cheaper Ga2O3was selected as gallium source, C as reducer and Zn as an evaporation accelerant, which has lower sublimation temperature. GaN nanoneedles can be deposited easily on the Si substrate located in the position of17cm from the center of the furnace. There is an absorption peak in the figure of Photoluminescence Spectra of the nanoneedle at the374nm wavelength. The GaN nanoneedles can emit ultraviolet.(3) The compact GaN film can be deposited on Si substrates at the temperature of1125℃and the vacuum of342Torr when Ga2O3was selected as gallium source, NH3as nitrogen source and Ar as carrier gas. However, the compact and less-defect GaN film can be deposited on Si substrates only at the temperature of1050℃by using the Sublimation Sandwich Method. Hexagonal prism GaN crystal growth along the direction of [0001] was deposited on the side of Si substrate. The growth mechanism of GaN film is island domain growth.(4) The compact Ga2O3films can be deposited on the Si substrate located in the postion of16cm from the center of the furnace at the temperature of950℃as the cheaper Ga2O3powder was selected as gallium source, the vacuum was608Torr, the reaction time was60min, the flow rates of H2and N2were25and100sccm, respectively.Ga2O3microspheres with novel structures were also synthesized.