Improvement of GaN crystalline quality on nanoscale patterned sapphire substrates

A method for the reduction of defect density in GaN epilayer using nanoscale patterned sapphire substrates (NPSS) was proposed. The sapphire substrates were patterned by natural lithography and inductively coupled plasma reactive ion etching (ICP-RIE). The undoped GaN films were grown on NPSS through metal organic chemical vapor deposition. The pits density was analyzed by atomic force microscope (AFM) and threading dislocation distribution was observed by scanning electron microscopy (SEM). The optical characteristics were measured from X-ray diffractometry and photoluminescence spectroscopy. These results indicate NPSS can improve crystalline quality by effectively reducing threading dislocations.