Controlled morphology of regular GaN microrod arrays by selective area growth with HVPE

• GaN microrods have been grown on patterned GaN/sapphire templates by hydride vapor phase epitaxy (HVPE).
• An excessive concentration of H2 in the carrier gas inhibits GaN growth.
• Optimized the carrier gas ratio is necessary to form 3D microstructure.
• No yellow band emission was observed by cathodoluminescence (CL) at low temperature.

The selective area growth (SAG) of GaN was implemented on patterned GaN/sapphire templates by hydride vapor phase epitaxy (HVPE) to fabricate regular arrays of Ga-polar GaN microrods. The control of growth parameters such as H2/N2 carrier gas ratio, growth temperature, and absolute NH3/HCl gas flow resulted in changes in the growth morphology. In particular, for an optimized mixed-carrier gas ratio of H2 to N2, we achieved vertically well-aligned microrods. The topmost regions of the GaN microrods were terminated with pyramidal facets, indicating typical Ga polarity. The optical properties of the grown microrods were characterized by cathodoluminescence (CL) at a low temperature. This revealed that the GaN microrods had high crystal quality since they exhibited suppressed yellow luminescence as well as strong band edge emission.