Effect of In Diffusion on the Property of Blue Light-Emitting Diodes

In diffusion to blue light-emitting diode (LED) wafers is performed by the inductive coupled plasma (ICP) treatment of a covering layer of indium tin oxide (ITO) on the wafer surface. The electrical property of the p-type contact is improved and the redshift of photoluminescence (PL) from the InGaN quantum well of the wafer is found. Measurements by x-ray photoelectron spectroscopy (XPS) demonstrate that In atoms have diffused into p-GaN. Reflectance spectra of the sample surface reveal the variation caused by the ICP treatment. A model of compensation of the in-plane strain of the InGaN layer is used to explain the redshift of the PL data. Finally, LEDs are fabricated by using as-grown and ICP-treated wafers and their properties are compared. Under an injection current of 20 mA, LEDs with ICP-induced In doping show a decrease of 0.3 V in the forward voltage and an increase of 23% in the light output, respectively.