Enhanced efficiency of CdMgZnSe down-converted light emitting diodes using light extraction features fabricated by laser-speckle lithography

Abstract

We report a method of making a wavelength converted, light-emitting diode (LED) having light extraction features based on coherent speckle patterns. These patterns have random feature size, random feature distribution, and random feature shape. The features were produced using a maskless lithography process based on exposing photoresist with a laser-induced coherent optical speckle pattern. A wet chemical etching process was then used to transfer the resist pattern into the underlying surface of the semiconductor wavelength converter layer. The external quantum efficiency of a wavelength converter with emitting surfaces having such extraction features showed a twofold increase compared to a wavelength converter without extraction features. While demonstrated here using semiconductor wavelength converters, this approach could also be applied to light extraction in conventional LED structures.