The morphology evolution of selective area wet etched commercial patterned sapphire substrates.

Patterned sapphire substrates (PSS) have been widely used to enhance the light output power of light emitting diodes (LEDs).The morphology and shape of the PSS have a great influence on the performance of the LEDs. In this work, commercial PSS is reprocessed utilizing selective-area wet etching approach, in which selective-area SiO2 mask is fabricated through partial exposure lithography instead of conventional overlay lithography. By precisely controlling the exposure time, the etching process can be controlled to take place only on the top of the PSS. Various surface morphology including pyramid, volcano, clover and closed-packaged inverted pyramid can be attained from the evolution of the selective-area etched PSS. The mechanism of the selective-area etched sapphire is correlated to the slant angle of the pattern surface and the SiO2 mask pattern. [ABSTRACT FROM AUTHOR]