The aim of this work is to determine diffusion coefficient of silicon in gallium nitride under different annealing conditions. Silicon was implanted into 3 µm thick GaN layer deposited on sapphire substrate with MOVPE (Metalorganic Vapour Phase Epitaxy) method. Implantation was performed at room temperature to a dose of 6×10 15 /cm 2 at energy of 100 keV. The samples were annealed under 1 atm nitrogen pressure at 900-1200 °C with or without an AlN protective layer. The extent of diffusion of the implanted species was characterized using the SIMS (Secondary Ion Mass Spectrometry) technique. The resultant concentration profiles are characterized with two diffusion fronts: slow diffused Si atoms at high concentration and fast diffused Si atoms at low concentration. We ascribe the first mechanism as to originate from diffusion in the crystal bulk (substitutional migration), while the second one -from diffusion via grain boundaries/dislocations. Si diffusion coefficient in a crystal was found to be dependent on annealing conditions, in contrast to diffusion via grain boundary. Calculated diffusion coefficient parameters for annealing with and without AlN layer amount respectively to: D O = 6.5×10-11 cm 2 /s, E a = 0.89 eV and D O = 9.1×10 -8 cm 2 /s, E a = 1.55 eV.
The crystallographic structures of the various Metalorganic Vapour Phase Epitaxy (MOVPE) thin GaN epitaxial layers deposited on (00.1) sapphire substrates are described and compared with the structural properties of the thick gallium nitride layers deposited by Hydride Vapour Phase Epitaxy (HVPE) on the top of them. The crystallographic structure and the quality of epitaxial GaN layers obtained in this way are determined. Additionally thick HVPE GaN layers deposited on these composite substrates (MOVPEGaN/sapphire) are compared with the thick HVPE GaN layers grown directly on sapphire substrates. It was found that HVPE thick GaN epilayers on sapphire are comparable with the HVPE thick GaN layers deposited on composite substrates.
Thick GaN layers deposited in HVPE system on composite substrates made on sapphire substrates in Metalorganic Vapour Phase Epitaxy (MOVPE) system have been investigated. The following substrates were used: (00.1) sapphire substrates with AlN, AlN/GaN and GaN thin layers. The crystallographic structure and the quality of the epitaxial thick GaN layers were determined. Comparison of the three types of thick layers was performed. Significant differences were observed. It was found that thick GaN deposited on the simplest MOVPE-GaN/sapphire composite substrate has comparable structure's properties as the other, more complicated.
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