In this work, the evolution of morphology and defect structure in GaN nucleation layers on the a-plane of sapphire are investigated using TEM. The growth temperature and pressure were varied from 560 to 1100°C and from 20 to 600 torr, respectively. Whereas the highest growth temperature leads to a continuous layer, a 2D growth mode is not attained when the chamber pressure is varied from 20 to 600 torr at 1028°C. At the highest pressures (>300 t orr), a large distribution is obtained for the island sizes.
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T W and PR acknowledge the support of the EU under contract number HPRN-CT-2001-0 0297
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Wojtowicz, T., Ruterana, P., Twigg, M. et al. The microstructure of GaN nucleation layers grown by MOCVD on (1120) sapphire versus pressure and temperature. MRS Online Proceedings Library 798, 508–511 (2003). https://doi.org/10.1557/PROC-798-Y5.32