The characteristics of high-voltage light-emitting diodes (HVLEDs) consisting of a 64-cell LED array were investigated by employing various LED structures. Two types of HVLED were examined: a standard HVLED with a single roughened indium tin oxide (ITO) surface grown on a sapphire substrate and a thin-film HVLED (TF-HVLED) with a roughened n-GaN and ITO double side transferred to a mirror/silicon substrate. At an injection current of 24 mA, the output powers of the HVLEDs fabricated using a sapphire substrate and those fabricated using a mirror/silicon substrate were 170 and 216 mW, respectively. Because the TF-HVLED exhibited improved thermal dissipation and light extraction, it produced a greater output power than the HVLED fabricated using the sapphire substrate did.