Nanoscale lateral epitaxial overgrowth of GaN on Si (111)

摘要

We demonstrate that GaN can selectively grow by metalorganic chemical vapor deposition into the pores and laterally over the nanoscale patterned SiO_2 mask on a template of GaN/AlN/Si. The nanoporous SiO_2 on GaN surface with pore diameter of approximately 65 nm and pore spacing of 110 nm was created by inductively coupled plasma etching using anodic aluminum oxide template as a mask. Cross-section transmission electron microscopy shows that the threading-dislocation density was largely reduced in this nanoepitaxial lateral overgrowth region. Dislocations parallel to the interface are the dominant type of dislocations in the overgrown layer of GaN. A large number of the threading dislocations were filtered by the nanoscale mask, which leads to the dramatic reduction of the threading dislocations during the growth within the nano-openings. More importantly, due to the nanoscale size of the mask area, the very fast coalescence and subsequent lateral overgrowth of GaN force the threading dislocations to bend to the basal plane within the first 50 nm of the film thickness. The structure of overgrown GaN is a truncated hexagonal pyramid which is covered with six {1101} side facets and (0001) top surface depending on the growth conditions.