Roughening surface morphology on free-standing GaN membrane with laser lift-off technique

Abstract

An ultraviolet (UV) laser lift-off (LLO) technique was presented to form a roughened surface morphology on GaN membrane grown by metalorganic chemical vapor deposition (MOCVD). The etched surface showed cone-like structures on a free-standing GaN membrane. Based on the scanning electron microscopy (SEM) and atom force microscopy (AFM) measurements, the etching mechanism was proposed, which was related to the different decomposition depth caused by the dislocations in the GaN membrane. The etching efficiency and morphology of GaN by the LLO technique and the photoelectrochemical (PEC) wet etching technique was compared and analyzed. This roughed cone-like surface morphology by LLO can enhance the external efficiency of vertical structure n-side-up GaN-based light-emitting diodes (LEDs) simultaneously while being released of the performance constrains impeded by sapphire.