Improvement in performance of GaN-based light-emitting diodes with Indium tin oxide based transparent ohmic contacts

InGaN/GaN multi-quantum well (MQW) light-emitting diodes (LEDs) with Indium tin oxide (ITO) and Ni/Au p-contacts have been successfully fabricated. ITO (500 nm) and Ni/Au (2 nm/9 nm) films were deposited onto p-GaN epitaxial layers by e-beam evaporation system. For the LEDs with in situ annealed ITO and Ni/Au contacts, the 20 mA forward voltage was 3.5 V and 3.2 V, respectively. Moreover, under the same amount of injection current, the LED with in situ annealed ITO p-contact had higher output electroluminescence (EL) intensity and larger light output power. The ITO processing enhanced the light output power by 60% compared to the Ni/Au processing. The light output and power conversion efficiency of ITO LEDs on GaN were greatly improved at high injection currents. The fabricated LEDs were subjected to a stress test at 30 mA and 55°C and showed very small degradation of optical power (< 1% decrease) for 24 hrs stress. The light output of MQW LEDs keeps 80% of the original value after 1000 hrs stressing. The fabricated LED devices have demonstrated a good reliability.