Title :
Light Extraction Efficiency and Radiation Patterns of III-Nitride Light-Emitting Diodes With Colloidal Microlens Arrays With Various Aspect Ratios
Author :
Li, Xiao-Hang ; Song, Renbo ; Ee, Yik-Khoon ; Kumnorkaew, Pisist ; Gilchrist, James F. ; Tansu, Nelson
Author_Institution :
Dept. of Electr. & Comput. Eng., Lehigh Univ., Bethlehem, PA, USA
fDate :
6/1/2011 12:00:00 AM
Abstract :
The fabrication studies of silica/polystyrene (PS) colloidal microlens arrays with various aspect ratios were performed on the III-nitride light-emitting diodes (LEDs). The use of colloidal-based microlens arrays led to significant enhancement in light extraction efficiency for III-nitride LEDs. In varying the aspect ratios of the microlens arrays, the engineering of various PS thicknesses was employed by using high-temperature treatment and redeposition process. The effects of PS thickness on the light extraction efficiency and far-field emission patterns of InGaN quantum-well (QW) LEDs were studied. The total output powers of microlens LEDs with various PS thicknesses exhibited 1.93-2.70 times enhancement over that of planar LEDs, and the use of optimized PS layer thickness is important in leading the enhancement of the light extraction efficiency in large angular direction.
Keywords :
III-V semiconductors; gallium compounds; indium compounds; light emitting diodes; microlenses; optical arrays; semiconductor quantum wells; wide band gap semiconductors; InGaN; aspect ratio; colloidal microlens arrays; layer thickness; light extraction efficiency; light-emitting diodes; quantum-well LED; radiation patterns; redeposition process; Annealing; Fabrication; Lenses; Light emitting diodes; Microoptics; Scanning electron microscopy; Suspensions; III-Nitrides; far-field radiation; light extraction efficiency; light-emitting diodes (LEDs); microlens arrays;
Journal_Title :
Photonics Journal, IEEE
DOI :
10.1109/JPHOT.2011.2150745
