By using iodine gas-assisted focused ion beam etching, a gallium nitride light-emitting diode with wave-patterned sidewalls and a microlens array on a p-GaN layer was successfully fabricated without an additional lithography process. The gallium nitride light-emitting diode after gas-assisted focused ion beam etching on the sidewalls and p-GaN layer shows 24% enhancement from the sidewalls and 53% from the top surface in optical output power with an operating voltage increase of 0.06 V at 20 mA.