Evolution of threading dislocations in GaN epitaxial laterally overgrown on GaN templates using self-organized graphene as a nano-mask

Growth of high-quality GaN within a limited thickness is still a challenge, which is important both in improving device performance and in reducing the cost. In this work, a self-organized graphene is investigated as a nano-mask for two-step GaN epitaxial lateral overgrowth (2S-ELOG) in hydride vapor phase epitaxy. Efficient improvement of crystal quality was revealed by x-ray diffraction. The microstructural properties, especially the evolution of threading dislocations (TDs), were investigated by scanning electron microscopy and transmission electron microscopy. Stacking faults blocked the propagation of TDs, and fewer new TDs were subsequently generated by the coalescence of different orientational domains and lateral-overgrown GaN. This evolution mechanism of TDs was different from that of traditional ELOG technology or one-step ELOG (1S-ELOG) technology using a two-dimensional (2D) material as a mask.