The epitaxial growth of GaN on Si substrates opens the possibility of integrating GaN and Si technologies. However, the 17% lattice mismatch generates dislocations reducing the quality of the grown GaN. To improve the layer quality, a procedure based on the formation of pressurized He bubbles in Si substrate was suggested earlier [1]. The bubbles attract the misfit dislocations formed at Si/GaN interface and redirect them towards the Si substrate, thereby reducing the dislocation density in the GaN layer. In this work we tried to determine the implantation conditions and annealing temperature to ensure bubble stability for Ne and He-Ne. We have implanted the Ne ions up to fluences of 5 × 10¹⁴ cm^-2, 1 × 10¹⁵ cm^-2 and 5 × 10¹⁵ cm^-2, as well as Ne co-implanted with He up to fluences of 5 × 10¹⁵ cm^-2 and 1 × 10¹⁶ cm^-2, respectively. Subsequently, these samples were subjected to rapid thermal annealing ranging from 400°C to 1000°C. RBS/Channeling measurements suggested a greater stability of some bubbles containing Ne (in the range of 800 - 900°C). TEM measurements, however, demonstrated that bubble morphology of He-Ne was similar to that of the pure Ne system, with a much higher residual implantation damage, even in the case of He:Ne co-implantation ratio of 10:1. In addition, a very weak stress field was observed around the bubbles suggesting an unpressurized system.

[1] Z. Liliental-Weber, R.L. Maltez, J. Xie, H. Morkoç, Journal of Crystal Growth, 310 (2008) 3917.