We investigated the influence of passivation structure on reverse leakage current characteristic of vertical GaN-based light emitting diodes (LEDs). Proper passivation structure is important for high-performance vertical LEDs because large external or residual stress arising during device fabrication and operation can deteriorate electrical properties such as leakage current and currentvoltage behavior. Unpassivated and SiO2-passivated vertical LEDs showed relatively large leakage currents in reverse bias. In contrast, photoresist-passivated vertical LEDs showed a very low leakage current of similar to 4 nA for a reverse bias of -5 V, and lower forward operation voltage of 3.22-3.24 V at 20 mA compared to lateral LEDs. (c) 2007 The Electrochemical Society.