Influence of Pre-Nucleation on Growth of GaN Low Temperature Layer on Sapphire Substrate
-
-
Abstract
Metal-organic chemical vapor deposition (MOCVD) technology is based on the thermal decomposition of gas source, which is suitable for large-scale production and is the main preparation method for growing semiconductor materials. In the process of GaN growth by MOCVD, the initial conditions on the substrate surface directly affect the nucleation and growth of the material, so it is critical for epitaxial growth. In this paper, the effect of sapphire substrate surface prenucleation on GaN nucleation at low temperature during GaN epitaxial growth was studied. By comparing the annealed morphology of the low-temperature layer grown on untreated samples and samples with high temperature prenucleation of TMGa and NH3, and samples with high temperature prenucleation of TMAl and NH3, we found that the nucleation point formed by high temperature prenucleation is conducive to attracting the surrounding gas source into the site and reducing the density of the nucleation island. Combined with optical real-time reflectance monitoring the nucleation process of grains in vapor deposition, a further lateral comparison shows that AlN is more stable at high temperature, and the prenucleation effect is better, which has a more significant impact on the morphology of GaN islets after annealing. The crystal quality of the nucleated layer was characterized by X-ray diffraction, and it was found that the (002) half-height width of the diffraction peak of the annealed nucleated layer could be reduced from 1636 arcsec to 1088 arcsec. Through comparative analysis, we believe that the advantages of high temperature prenucleation process may come from its ability to improve the crystalline orientation of small islands at the early stage of nucleation. These studies provide new process ideas for further improving the epitaxial quality of GaN.
-
-