To integrate multiple functional devices on a chip, advances in epitaxial growth on heterosubstances are required. As one approach to achieve an epitaxial layer on an amorphous substrate, we developed a method of combined epitaxial growth using molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD). This two-stage combined growth can be used to grow a binary gallium nitride (GaN) on any thermally durable substances. The first MBE growth step provided us effective nucleation with uniform morphology. Meanwhile, the second MOCVD growth enabled improved crystalline quality. Detailed analysis at grain-to-grain and layer-to-layer interfaces was studied with high-resolution transmission electron microscopy (TEM) characterization. This study gives a deep understanding of the growth behavior, thereby supporting the demonstration of perfect single crystalline GaN, enabling the realization of optoelectronic GaN-based devices on amorphous layer.

Microscale platelet-shaped GaN grains were grown on amorphous substrates by a combined epitaxial growth method of molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD). First, MBE GaN was grown on an amorphous substrate as a pre-orienting layer and its structural properties were investigated. Second, MOCVD grown GaN samples using the different growth techniques of planar and selective area growth (SAG) were comparatively investigated by transmission electron microscopy (TEM), cathodoluminescence (CL), and photoluminescence (PL). In MOCVD planar GaN, strong bound exciton peaks dominated despite the high density of the threading dislocations (TDs). In MOCVD SAG GaN, on the other hand, TDs were clearly reduced with bending, but basal stacking fault (BSF) PL peaks were observed at 3.42 eV. The combined epitaxial method not only provides a deep understanding of the growth behavior but also suggests an alternative approach for the growth of GaN on amorphous substances.