Technology Development for Production of Gallium Nitride Templates on Sapphire Substrate with Reduced Dislocation Density

This article considers issues related to the development of technology for producing gallium nitride templates with a reduced dislocation density on a sapphire substrate. The authors assembled and launched a complex of MOCVD equipment and set up control systems for the growth of in situ structures. Optimum technological modes for the step-by-step production of gallium nitride buffer layers on a sapphire substrate have been developed. These modes include substrate preparation by annealing and nitridation, growth of gallium nitride nucleation layers with their subsequent annealing, coalescence of a single-crystal layer, formation of a buffer layer with the required thickness, properties and doping levels based on various technological approaches to the formation of the nucleation layer. Experimental samples with a smooth, planar surface were obtained: with a pulsed supply of trimethylgallium, the thickness of the grown layer was 2.7–2.8 μm at a growth rate of 1.1 μm/h, full width at half maximum of the diffraction peak is 570 arcsec, the dislocation density is 2.7 × 107 cm–2; with a continuous supply of trimethylgallium, the thickness of the grown layer was 2.7–2.8 μm, the growth rate was 2.8 μm/h, full width at half maximum of the diffraction peak of 608 arcsec, the dislocation density was 5.1 × 107 cm–2, the electrical properties of this material were: n-type, carrier concentration was n = 1.0 × 1017 cm–3, carrier mobility μ = 113 cm/Vs. Good correlation is observed between the results of thickness and surface morphology studies on SEM and in-situ structure growth monitoring systems. It is shown that the obtained samples in defect density and basic characteristics correspond to commercial templates of gallium nitride grown on sapphire substrate, presented in the world market.