Nano-patterned AlGaInP light-emitting diode based on UV-Kiss metal transfer technology

This paper describes a new nano-patterning technique, the UV-Kiss Metal Transfer (UV-KMT) method, and applies it for patterning micro/nano-structures on AlGaInP light-emitting diodes (LEDs) for enhancing their light extraction efficiency. First of all, an ETFE mold with micro/nano-features is replicated from a silicon master mold. A thin metal film is then deposited on the ETFE mold which has very low surface energy. A layer of UV curable polymer solution is spin-coated on an AlGaInP LED surface. The metal-film coated EFTE mold and the UV-polymer coated LED are brought into contact with a uniformly distributed pressure of 0.1 MPa, and UV light is radiated through the ETFE mold and solidifies the UV polymer. The solidified UV polymer has stronger adhesion to the metal film in contact with, and therefore can transfer the metal pattern defined by the convex surface feature of the ETFE mold onto the AlGaInP LED surface. The transferred metal pattern is then serving as an etching mask for RIE etching on the underlying UV polymer layer. Finally, a patterned structure consisting of a metal film on top and an underlying UV polymer layer is formed on the LED surface. This metal/polymer surface structure can well serve as an etching mask again for ICP etching on the LED, and hence complete the fabrication of micro/nano-structures on the top surfaces of AlGaInP LEDs for enhancing their light extraction efficiency. The optical power measurement using an integrating sphere shows that the extraction efficiency of the patterned LED is 25% higher than that of the conventional LED. In short, we demonstrate an easily implemented, cost effective, and powerful method to pattern LED substrate.