The Synthesis And Properties Of GaN Materials By CVD Method

As the representative of the third generation direct wide band gap semiconductor materials,GaN has the advantages of high breakdown field,high mobility,high electron saturation drift rate,high frequency,high temperature resistance and anti radiation,which makes it suitable for new generation of soild-state lighting,detectors,microwave radio frequency devices and power electronic devices.GaN materials with multiple morphologies,such as nanowires,nanotubes,nanobelts,nanosheets,nanotrees and films,have been obtained by various methods.GaN with different morphologies and structures have a significant effect on their performance and application.Therefore,the controllable synthesis of GaN nanomaterials,films and nanocomposites with different morphologies and structures is still a hot research topic.In this paper,the controllable growth of GaN nanowires and thin films has been realized on the sapphire substrate and the GaN/SiO_xN_y nanocomposites have been synthesized on Si substrate by chemical vapor deposition(CVD).Their morphological structures,compositions,growth mechanisms and luminescence properies were characterized and analyzed.The main research results are as follows:(1)High-quality GaN nanowires with simultaneous integration of the N-polar and knots have been successfully synthesized on c-plane sapphire substrates via a simple and effective chemical vapor deposition method through the nitriding treatment of NH₃ on the substrate surface as well as VS growth mechanism.The effects of Ga concentration and different planes of sapphire substrate on its morphology and structure were investigated,and its growth mechanism was analyzed in detail.(2)The simultaneous epitaxial growth of polar c-oriented horizontal GaN nanowire arrays(Au-free region)and nonpolar a-plane GaN thin films(Au-coated region)has been realized by controlling the Au-coated region on the r-plane sapphire substrate.The size of the nanowires and the morphology of the films were controlled by changing the growth time and the thickness of the Au films.The growth orientation of nanowires and thin films was controlled by sapphire substrates with different planes.The epitaxial relationship among horizontal nanowires,films and substrates was analyzed.(3)The self-patterned epitaxial growth of strain-free GaN films on c-plane sapphire substrate has been achieved through Au initializing the nucleation of the inverted hexagonal GaN pyramid grown in four directions.The effect of growth temperatures on its morphological structure was investigated.Its growth process was also analyzed.(4)The synthesis of high-density jellyfish-like GaN/SiO_xN_y nanocomposites with GaN nanobloks as the top-caps and SiO_xN_y nanowires as the bottom-tentacles on Si substrate has been achieved through the Ga droplets catalytic growth of silica nanowires and the nitriding treatment of silica nanowires with Ga balls by NH₃.The inflence of growth temperatures on its morphology and structure was discussed and the growth mechanism was analyzed.