Enhanced Efficiency Of Cdmgznse Down-Converted Light Emitting Diodes Using Light Extraction Features Fabricated By Laser-Speckle Lithography

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. (c) 2010 American Institute of Physics. [doi: 10.1063/1.3524024]