Thermal annealing effect of indium tin oxide contact to GaN light-emitting diodes

We have fabricated GaN-based light-emitting diodes (LEDs) using transparent indium tin oxide (ITO) for p-type contacts. The current-voltage (I-V) characteristics of the devices have been studied. When annealed at 700°C, the p-n junction of the diodes became very leaky, and even electrical short circuits have been observed. According to scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometer analyses (EDS), it was found that indium (In) diffused into the LED structure with defects such as threading dislocations (TDs) or V-pits. The defects provide leakage paths to cause short circuits in p-n junctions at high annealing temperatures.