Synthesis And Properties Of GaN And The Doped GaN

GaN is an excellent Ⅲ-Ⅴ compound semiconductor material with wide band gap. Due to its favorable chemical and physical stability, it has a wide range of commercial applications and has attracted great interest and attention. In this dissertation, we fabricated micro/nanoscale GaN by CVD and studied the effects of N2flow, NH3flow, substrate, metal buffer layer, temperature, reaction time and dopant (Mn、Cu) on the structures, morphologies, optical and electrical properties of GaN micro/nanomaterials. Furthermore, the possible formation mechanisms of GaN micro/nanomaterials is proposed. The main research results are as follows:1. GaN micro/nanomaterials were synthesized by chemical vapor deposition (CVD) with metal Ga and NH3as raw materials. The morphology, composition, crystal structure and properties of GaN were studied under different conditions. The conclusions are as follows:(1) With the increase of N2flow rate, the morphology of GaN evolved from microrods to vermicular-like wires and finally to smooth nanowires. All samples are hexagonal wurtzite, showing near-band-edge UV emission peaks of383nm and blue light emission peaks of about470nm.(2) All samples are hexagonal wurtzite under different NH3flow rate, and appeared near-band-edge UV emission peaks around380nm and blue light emission peaks with larger FWHM and center wavelength of460nm. At the NH3flow rate of30sccm, the products have best crystalline properties and uniformer diameter and smoother surface.(3) The GaN microfilms grown on Al、Ni and Fe metal buffer layers are hexagonal wurtzite, showing strong near-band-edge UV emission peaks and red light emission peaks with center wavelength of672nm. Their values of resistance and mobility are RNi<RFe<RAl and μNi<μFe<μAl, respectively. The products on Ni buffer layer have uniform morphology and best crystallinity and optical properties.(4) The GaN microsheets grown on both Si(100) and sapphire substrates are hexagonal wurtzite and n-type, but the products on sapphire substrate have smoother surfaces and best crystallinity and optical properties.(5) All samples grown at different temperatures are hexagonal wurtzite, showing near-band-edge UV emission peaks at361nm and red light emitting peak at646nm, while the products grown at950℃have uniform diameter of about100nm, best crystallinity and optical properties.(6) The products with reaction of30min show best morphology, crystallinity, optical properties and uniform diameter during the process of reaction time increasing from15min to45min.2. With the doping amount of Mn increasing from4%to16%, the morphology of GaN evolved from microrods to microtubes, together with a redshift of the near band edge UV emission peaks. When the doping amount of Mn reach to12%, the products have uniform morphology, best crystallinity and optical properties. While the Cu-doped products have best morphologies and properties when the doping amount of Cu increases to6%.