Light extraction efficiency and radiation patterns of III-nitride light-emitting diodes with colloidal microlens arrays with various aspect ratios

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 1.932.70 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. © 2011 IEEE.