Search

We report on the structuring of the backside surface of sapphire substrates in high-power flip-chip light-emitting diodes (LEDs) by femtosecond laser direct writing. Varying the laser powers has been found to affect the sizes of the inscribed patterns on a submicron scale which facilitates the control of the structure sizes with high precision. Accordingly, since on the one hand the light extraction efficiency reveals a strong dependence on pattern sizes, and on the other hand, femtosecond laser structuring provides a simple opportunity to inscribe diverse structures along the LED surfaces, LEDs with laterally controlled light extraction efficiencies can be fabricated. [ABSTRACT FROM AUTHOR]

Abstract: We report on a wealth of possibilities femtosecond (fs-) laser processing provides for future advancements of device efficacy and white light quality of light-emitting diodes (LEDs) for solid state lighting applications. We discuss three different processing approaches, subtractive, volume and additive structuring, as well as their individual applicabilities and advantages with respect to locally controlled enhancement of light-extraction, modification of the light distribution and adjustment of a desired colour temperature in phosphor conversion based white LEDs. [Copyright &y& Elsevier]