Lithographic technologies suitable for PhC patterning and optical properties of patterned LED surfaces

There are several promising methods for photonic crystal (PhC) patterning of LED surfaces for improving the LED efficiency, i.e. the light out coupling. 2D patterns with different periods and various symmetries were fabricated using interference lithography (IL), non-contact near-field scanning optical microscopy (NSOM) lithography, and e-beam direct write (EBDW) lithography, respectively. The periodicity and quality of fabricated structures have been investigated using AFM and SEM imaging. Light extraction enhancement (LEE) was studied by measuring of the light-current (L-I) characteristics of untreated reference LEDs and patterned LEDs. The highest achieved LEE was measured for LEDs patterned by interference lithography.