Efficacy of single and double SiN x interlayers on defect reduction in GaN overlayers grown by organometallic vapor-phase epitaxy

• Published in: Journal of applied physics 2005-12, Vol.98 (12), p.123502-123502-8
• Main Authors: Yun, F., Moon, Y. -T., Fu, Y., Zhu, K., Ozgür, Ü., Morkoç, H., Inoki, C. K., Kuan, T. S., Sagar, Ashutosh, Feenstra, R. M.
• Format: Article
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.2142074

We report on the growth of and evolution of defects in GaN epilayers having single- and double-layer SiN x nanoporous insertion layers. The SiN x was formed in situ in the growth chamber of an organometallic vapor-phase epitaxy system by simultaneous flow of diluted silane and ammonia. The GaN epilayers and SiN x interlayers were grown on 6 H - SiC substrates using three different nucleation layers, namely, low-temperature GaN , high-temperature GaN , and high-temperature AlN nucleation layers. X-ray-diffraction rocking curves and cross-sectional and plan-view transmission electron microscope analyses indicated that a nanoporous SiN x layer can reduce the dislocations density in the GaN overgrown layer to ∼ 3 × 10 8 cm − 2 range; below this level the defect blocking effect of SiN x would saturate. Therefore the insertion of a second SiN x layer becomes much less effective in reducing dislocations, although it continues to reduce the point defects, as suggested by time-resolved photoluminescence measurements. The insertion of SiN x interlayers was found to improve significantly the mechanical strength of the GaN epilayers resulting in a much lower crack line density.