Enhanced light-extraction from a GaN waveguide using micro-pillar TiO2SiO2 graded-refractive-index layers

• Published in: Physica status solidi. A, Applications and materials science Vol. 209; no. 11; pp. 2277 - 2280
• Main Authors: Mont, Frank W., Fischer, Arthur J., Noemaun, Ahmed N., Poxson, David J., Cho, Jaehee, Schubert, E. Fred, Crawford, Mary H., Koleske, Daniel D., Fullmer, Kristine W.
• Format: Journal Article
• Language: English
• Published: Berlin WILEY-VCH Verlag 01.11.2012; WILEY‐VCH Verlag
• Subjects: GaN; GRIN; light-extraction; micro-pillars
• ISSN: 1862-6300; 1862-6319
• DOI: 10.1002/pssa.201228295

A GaN waveguide structure with micro‐pillar arrays is designed and fabricated to measure the extraction of optical modes that would be waveguided in the absence of the pillars. Electroluminescence (EL) measurements of waveguide light‐emitting diodes (LEDs) with pillar diameters in the 2–10 µm range revealed increasing light‐extraction efficiency (LEE) enhancement with decreasing pillar diameter. Ray tracing simulations of LED far‐field patterns confirmed experimental trends. A 54% enhancement is demonstrated for GaN waveguides cladded with a triangular lattice of graded‐refractive‐index (GRIN) TiO2SiO2 micro‐pillars of 2 µm diameters compared to GaN waveguides cladded with an unpatterned GRIN TiO2SiO2 layer.