COMMUNICATION TECHNOLOGY ed by sapphire. 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 imped laser lift-off, roughening, GaN, chemical wet etchThere are numerous applications for GaN-based optoelectronic and electronics devices. High efficiency GaN-based light-emitting diodes (LEDs) are one of the most important applications, which can be used in many fields including full-color displays, green traffic lights, and flat-panel room lighting to replace incandescent and fluorescent fixtures [1,2] . However, the total light output from these LEDs is still rather low. The internal quantum efficiency has already reached about 90% by improving the crystal quality and epitaxial layer structure. Much improvement can be achieved in the external quantum efficiency (η ext ), which is primarily limited by the total internal reflection of the light generated from the active region at the interface of the semiconductor and air. Texturing the top surface of a LED is the most well known method to improve the light extraction among many methods [3][4][5][6] . A dry etching method was employed on top of the LED using a mask for texture patterning [7,8] . In this case, serious damage can be induced due to the formation of surface defects such as vacancies, impurities and residuals by the dry etching process. Thus, many researchers have attempted to replace the dry etching process with a wet etching process for texturing the surface. Photoelectrochemical (PEC) wet etching has been demonstrated to provide a broad and smooth etched surface with a vertical anisotropic profile [9,10] . However, three disadvantages of PEC etching encountered in device fabrication are the lateral potential gradient on the GaN membrane, the narrow region of operation for a smooth etched surface and the incapability of etching p-GaN directly. The lateral potential gradient was present along the distance from the conducting electrode to the GaN membrane; a non-uniform depth of etching then occurred along the potential gradient.