Polarity- and Site-Controlled Metal Organic Vapor Phase Epitaxy of 3D-GaN on Si(111)

A site- and polarity-controlled MOVPE growth of 3D-GaN on Si(111) substrates is established using the polarity-dependent growth speed of GaN on an intermediate AlN layer. For hydrogenated Si or elevated AlN growth temperatures mixed-polar growth is observed. N-polarity could be realized on oxidized Si(111) surfaces by a reduced AlN growth temperature of T-AlN=930 degrees C. Specific Si crystal facets (e.g., {100}, {112}) are determined as starting points for metal-polar growth of AlN. By site-controlled etching in Si, we intentionally expose these additional crystal facets prior to epitaxy to obtain defined starting points for metal-polar growth. At T-AlN=930 degrees C, this leads to a site-controlled growth of metal-polar GaN, surrounded by N-polar AlN on Si(111). Thus both, a polarity- and site-controlled epitaxial growth of 3D-GaN is achieved. The new developed method has been applied to a large variety of structure sizes from 650nm to 1mm. The results are supported by a schematic model, explaining the influence of surface termination, in situ desorption, and growth conditions. This paves the way to the development of future 3D-opto-electronic devices, directly established on Si.