Light-extraction enhancement of GaInN light-emitting diodes by graded-refractive-index indium tin oxide anti-reflection contact

A study was conducted to demonstrate that oblique-angle deposition can be used to enhance the refractive index of a thin-film material, which is selected for its material and refractive index properties. It was demonstrated that these properties thin film materials allow the elimination of Fresnel reflection, which is one of the fundamental limitations in light-extraction efficiency of light-emitting diodes (LED). The study demonstrated that the limitation is overcome by fabricating coatings whose refractive index decreases from the refractive of the active semiconductor layer to the refractive index of the surrounding medium. It was also demonstrated that oblique-angle deposition is a method of growing porous thin films and thin films with low refractive index, enabled by surface diffusion and self-shadowing effects during the deposition process.