Improvement of the Electrical Properties of 450-nm-light-emitting Diodes by Surface Chemical Treatment

A chemical treatment process for improving the surface contact resistance of the p-GaN/Indium-tin-oxide interface in 450-nm-light-emitting diodes (LEDs) was investigated. For the surface treatment, indium metal was dissolved in H2SO4 solution with various concentrations. Process parameters such as p-GaN annealing temperature, annealing time, and cleaning were studied to optimize the surface treatment process. Surface analysis indicated that the chemical treatment has no effect on the surface morphology of the p-GaN layer. However the amount of Mg was reduced, and sulfur was found on p-the GaN surface after the treatment. Eventually, the operation voltage of the LEDs was drastically decreased by ~0.2 V, and the light output was improved by 16.0% at an injection current of 350 mA.