Light output enhancement for nitride-based light emitting diodes via imprinting lithography using spin-on glass

The production of micrometric imprinted structures made of spin-on glass (SOG) is demonstrated in this paper. Two different mold materials, sapphire and silicon, are fabricated by dry and wet etching for both 1-D and 2-D patterns. The imprinting pressure, the imprinting temperature, and anti-adhesive films are also discussed. Finally, the imprinted structures are integrated with the chip process of the light emitting diodes (LEDs) in order to understand how the output optical efficiency is affected by those embossed SOG structures. In our study, both the 1-D and 2-D surface structures proved to be useful in enhancing the light extraction efficiency. The output intensity of the 2-D micro-cylinder structure on LEDs increased to 26.2% compared with that of conventional LEDs. In addition, the forward voltage is almost kept identical under a 20 mA injection.