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Semiconductor light-emitting devices having concave microstructures providing improved light extraction efficiency and method for producing same

United States Patent

November 19, 2013
View the Complete Patent at the US Patent & Trademark Office
A conventional semiconductor LED is modified to include a microlens layer over its light-emitting surface. The LED may have an active layer including at least one quantum well layer of InGaN and GaN. The microlens layer includes a plurality of concave microstructures that cause light rays emanating from the LED to diffuse outwardly, leading to an increase in the light extraction efficiency of the LED. The concave microstructures may be arranged in a substantially uniform array, such as a close-packed hexagonal array. The microlens layer is preferably constructed of curable material, such as polydimethylsiloxane (PDMS), and is formed by soft-lithography imprinting by contacting fluid material of the microlens layer with a template bearing a monolayer of homogeneous microsphere crystals, to cause concave impressions, and then curing the material to fix the concave microstructures in the microlens layer and provide relatively uniform surface roughness.
Tansu; Nelson (Bethlehem, PA), Gilchrist; James F. (Allentown, PA), Ee; Yik-Khoon (Mountain View, CA), Kumnorkaew; Pisist (Bethlehem, PA)
Lehigh University (Bethlehem, PA)
12/ 963,098
December 8, 2010
STATEMENT REGARDING FEDERALLY-SPONSORED RESEARCH OR DEVELOPMENT This invention was made with government support under U.S. National Science Foundation--ECCS Award #0701421, US National Science Foundation--CBET Award #0828426, and US Department of Energy--NETL (DE-FC26-08NT01581). The government has certain rights in the invention.