The influences of contact interfaces between the indium tin oxide-based contact layer and GaN-based LEDs

We have fabricated GaN-based light-emitting diodes (LEDs) using transparent indium tin oxide-based (ITO-based) p contacts. The current-voltage characteristics and life tests of GaN-based LEDs have been studied. LED life tests showed that a pure ITO contact layer had poor reliability at high current stress. We also found that the GaN-based LED could achieve good reliability with a NiO/ITO contact layer. Using transmission electron microscopy and energy-dispersive X-ray spectrometer analyses, we observed In-contained metallic interface between the p-GaN layer and the pure ITO contact layer after annealing at 600 degrees C. It revealed that ITO would react at interface or indiffuse near the interface at 600 C. The LED was degraded with unstable interfaces after life tests (stressed by a 50-mA current injection). To improve the reliability of GaN-based LEDs with the ITO contact layer, we suggest that the NiO layer be used to prevent the reaction and block the leakage pathway. (c) 2006 The Electrochemical Society.