Vertical GaN-based light-emitting diodes (LEDs) were fabricated using a laser-liftoff process and the effect of the cathode processing conditions on the properties of the LEDs was investigated. Surface roughening by 10% Cl2/90% BCl3 plasma etching improved the light emission intensity at an operating current of 20 mA; however, the forward operating voltage was increased due to the thin and rough n-GaN layer. The use of an indium tin oxide (ITO) contact on the roughened n-type GaN surface decreased the forward voltage significantly, by decreasing the spreading resistance of the n-type GaN contact without decreasing the emission intensity. Through the combination of the ITO contact and the surface roughness of the n-GaN layer, a 100% increase in the extraction efficiency was obtained compared to that of a lateral GaN device, with maintaining a similar forward operating voltage.