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Synthesis of GaN-related Nanomaterials by Chemical Vapor Deposition

Author: LiMin
Tutor: ZhangBin
School: Northeastern University
Course: Materials Science
Keywords: GaN nanomaterials SiO_x nanostructures chemical vapor deposition(CVD) growth mechanism
CLC: TB383.1
Type: Master's thesis
Year: 2008
Downloads: 104
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Abstract


GaN, a typical representative of the third generation semiconductor materials, is one of the most promising materials for fabrication of blue-emitting diodes and high-power optoelectronic devices. Different from their corresponding bulk materials, GaN nanomaterials have a lot of characteristics, which are suitable for applications in visible and ultraviolet optoelectronic devices. In recent years, although much more attentions have been paid to the investigation of physical properties of low-dimensional GaN nanomaterials, less work is conducted on synthesise of GaN nanostructures. It is necessary for us to do the present research.Cheaper Ga2O3 was selected as gallium source, NH3 as nitrogen source, H2 as reducer and N2 as carrier gas. GaN nanostructures 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 following results are obtained.(1) The way of gas flow can affect the morphology and the composition of the synthesized products in the process of synthesis reaction. It is the best way for gases, including the reducer gas, the carrier gas and the gas of nitrogen source, to enter the reactor at the same time. Ideal grain GaN film can be obtained on the Si substrate when reducing gas H2 flows at the rate of 25sccm and N2 flows at the rate of 100sccm.(2) The location of the Si substrate is an important factor which affects the synthesized products. The zone of 13～21cm from the center of the furnace is the deposition area of the products. It is esay to grow one-dimentional GaN nanowires, GaN thin films and GaN/Ga2O3 films, respectively when the substrate located from the center of the furnace to far.(3) The compounds GaN/Ga2O3 with flower-like structure were obtained when the Si substrate was located at the lower temperature zone. The substances with flower-like structure are of rough surfaces. The nanobars which compose the "flowers" get wider and wider from the roots to the tops.(4) The reaction of Ga generated by the decomposition of Ga2O3 and the silicon substrate produced Ga-Si alloy. Following Vapor-Liquid-Solid (VLS) growth mechanism, catkin-shaped SiOx nanostructures can grow through the action of Ga self-catalysis.

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