Roughening Hexagonal Surface Morphology on Laser Lift-Off (LLO) N-Face GaN with Simple Photo-Enhanced Chemical Wet Etching

A photo-enhanced chemical wet etching technique is presented to form a roughened surface morphology with hexagonal symmetry on laser lift-off (LLO) N-face GaN grown by metalorganic chemical vapor deposition (MOCVD). An aqueous solution of KOH was used as etch electrolyte. The etched surface showed cones with hexagonal pyramid structures bound by {1011} facets. A detailed analysis of the etch rates and time-evolution of the surface morphology is described as a function of KOH concentration (1.25 M to 8.8 M). The comparison between (0001) N-face and Ga-face GaN etch morphology is discussed. This roughened hexagonal surface morphology can be applied to enhance the external efficiency in GaN based light-emitting diodes (LEDs).