InGaN/GaN multiple-quantum-well light-emitting diodes (LEDs) with peak emission at ∼405 nm were grown on bulk GaN and sapphire substrates using MOCVD. Tunneling current was found to be dominant in the LED on sapphire over a wide range of applied bias, but was substantially suppressed in the homoepitaxial LED. Nanoscale electrical characterization using conductive atomic force microscopy (C-AFM) revealed highly localized leakage current at V-defects in the LED structure on sapphire, indicating that the associated threading dislocations were electrically active and behaved as leakage current pathways connected across the p-n junction. Compared to the lateral LED on sapphire, the vertically-structured LED on GaN had a reduced series resistance of 7 Ω and greatly improved power conversion efficiencies. The homoepitaxial LED was subjected to stress test at 400 mA for 24 h and showed minimal optical degradation, whereas the same stress resulted in the destruction of the LED on sapphire due to increased current crowding and self-heating.